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UNIVERSITY OF GHANA COLLEGE OF BASIC AND APPLIED SCIENCE

BREEDING ECOLOGY AND FORAGING BEHAVIOUR OF BLACK-WINGED STILT (HIMANTOPUS HIMANTOPUS) IN GHANA

BY EMMANUEL NII ATTRAM TAYE (10381087)

A THESIS SUBMITTED TO THE SCHOOL OF GRADUATE STUDIES IN PARTIAL FULFILMENT OF THE AWARD OF DEGREE OF MASTER OF ZOOLOGY

DEPARTMENT OF ANIMAL BIOLOGY AND CONSERVATION SCIENCE

(MARCH 2019)

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DECLARATION

I Emmanuel Nii Attram Taye achieved this work independently under the supervision of Professors Yaa Ntiamoa-Baidu and Erasmus H. Owusu. I declare that except for other people’s investigations which have been duly acknowledged, this work is a result of my own original research, and this dissertation, neither in whole nor in part has been presented elsewhere for another degree.

……………………………… ……..……………………………..

EMMANUEL NII ATTRAM TAYE DATE

(STUDENT)

……………………………… ……..……………………………..

PROF YAA NTIAMOA-BAIDU DATE

(PRINCIPAL SUPERVISOR)

……………………………… ……..……………………………..

PROF ERASMUS H OWUSU DATE

(SUPERVISOR)

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DEDICATION

This work is dedicated to my mom Mrs. Love Betty Taye and my dad Mr. Lord

Joseph Taye who have sacrificed a lot to bring me this far. But for their wise counsel and calm leadership, I would not be here. They are my heroes.

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ACKNOWLEDGEMENT

My sincerest appreciations go to my Principal Supervisor Professor Yaa Ntiamoa-Baidu whose invaluable and blunt critique of my work has brought it to this stage and to my Co-supervisor

Professor Erasmus H. Owusu who kindled my love for biodiversity years ago during my first degree. My gratitude goes to Mr. Jones Kpakpa Quartey for always being a brother and source of both intellectual stimulation and emotional motivation; he has always been supportive of me. I owe tons of gratitude to the following persons for their immense assistance and support:

Mrs. Linda Tetteh, Mrs Leticia Taye, Mrs Hannah Amponsah-Mensah, Miss Patricia Afrifa,

Mr. Enoch Gbi; Mr. William Smith, Miss Sylvia Kyere, Miss Freda Okine, Miss Margaret

Impraim, and Miss Candace Owusu.

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Table of Contents DECLARATION ...... i DEDICATION ...... ii ACKNOWLEDGEMENT ...... iii LIST OF FIGURES ...... viii LIST OF TABLES ...... x ABSTRACT ...... xi CHAPTER ONE ...... 1 1.0 INTRODUCTION ...... 1 1.1 BACKGROUND ...... 1 1.2 Justification ...... 4 1.1 Research concept and key research questions ...... 6 1.1 Objectives ...... 7 Main objective ...... 7 CHAPTER TWO ...... 8 2.0. Literature review ...... 8 2.1 Wetlands ...... 8 Wetland fauna and flora ...... 13 Wetland degradation ...... 14 2.2. Breeding ecology...... 17 Breeding behavior ...... 17 Mate selection and copulation ...... 17 Site selection ...... 18 Black-winged Stilt Clutch size ...... 19 Parental care and incubation period ...... 20 Deterrent behavior ...... 20 Egg shell removal and egg capping...... 21 Sources of nest failure ...... 22 Nest monitoring and predation or nest success ...... 24 RUNT EEGGS ...... 25 2.3. Foraging ecology ...... 26 2.3.1. Time budget ...... 26 Foraging behaviour ...... 27 Diet of Black-winged stilts ...... 30

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Disturbance, aggression and territoriality ...... 31 Foraging location and time ...... 32 Foraging success and age ...... 33 Feeding techniques...... 33 CHAPTER THREE ...... 39 3.0. Materials and methods ...... 39 3.1 Study area ...... 39 3.1.1 Location and size ...... 39 3.1 Population and livelihoods ...... 40 3.1.1 Land use and ownership ...... 41 3.1 Climate ...... 43 3.1.1 Vegetation ...... 43 3.1.1 Faunal composition ...... 44 3.1.1 Geology and Soil ...... 44 3.1.1 Relief and drainage...... 45 3.1.1 Hydrology...... 45 3.1.1 Threats ...... 45 3.1 Methods ...... 46 3.1.1 Study site selection ...... 46 3.1.1 Breeding ecology ...... 46 3.1.1.1 Foraging ecology ...... 48 3.1.1 Time activity budget...... 50 3.1.1 Breeding ecology...... 51 3.1.1.1 Nest monitoring ...... 51 3.1.1.1 Nest success...... 52 3.1.1.1 Incubation period...... 52 3.2.3.4. Parental care ...... 53 3.2.3.5. Measurement of Egg Length, width and weight ...... 53 3.1.1 Foraging ecology ...... 54 3.1.1.1 Macroinvertebrate sampling ...... 54 3.1.1.1 Foraging behavior ...... 55 3.2. Data Analysis ...... 57 CHAPTER FOUR ...... 60

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4.0 Results ...... 60 4.1 Breeding ecology ...... 60 4.1.1 Nest construction ...... 60 4.1.2 Nest location ...... 63 4.1.2 Nest recycling ...... 63 4.1.2 Nesting Area properties ...... 63 4.2 Mating behavior ...... 65 4.3 Nesting behavior ...... 65 4.3.1 Brooding ...... 65 4.3.1 Nest protection ...... 66 4.3 Minimum permissible distance ...... 68 4.5 Clutch size, incubation period and nest success ...... 69 4.5.1 Clutch size ...... 69 4.5.1 Incubation period...... 71 4.5.1 Hatching success ...... 71 4.5.4 Parental care ...... 75 4.6 Biometric measurements of Black-winged Stilt eggs ...... 77 4.7 Factors influencing nest success ...... 84 4.8 Causes of nest failure and chick mortality ...... 86 4.9. Runt eggs ...... 87 4.10 Foraging Behavior ...... 88 4.10.1. Diurnal time-activity budget ...... 88 4.10.2 Prey of Black-winged Stilt and densities of macroinvertebrate ...... 91 4.10.3. Black-winged stilt foraging behavior ...... 93 4.2.4. Foraging style ...... 97 4.2.5. Feeding rates ...... 97 CHAPTER FIVE ...... 101 5.0 Discussion ...... 101 5.1. Breeding ecology ...... 101 5.1.2. Nesting behavior of Black-winged Stilts ...... 101 5.1.2. Hatching success and factors affecting hatching success...... 110 5.2. Foraging Behavior ...... 113 5.2.1. Diurnal activity patterns ...... 113

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5.2.2. Foraging habitats and water depth selection ...... 116 5.2.3. Black-winged Stilt Foraging style ...... 117 CHAPTER SIX: CONCLUSIONS AND RECOMMENDATIONS ...... 119 6.1. Conclusions ...... 119 6.2. Recommendations ...... 120 REFERENCES ...... 122 Appendices ...... 132 Appendix 1 ...... 132 Appendix 2 ...... 133

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LIST OF FIGURES Figure 3.1: Densu Delta Ramsar Site ...... 39 Figure 3.2: Map of Densu Delta Ramsar site showing settlements around and within the wetland ..... 42 Figure 3.3: Commercial salt mining (Image source: Daniel Domashie)...... 42 Figure 3.4: Sites at the Densu Delta Ramsar site used for Black-winged Stilt breeding studies ...... 48 Figure 3.5: Sites used by Black-winged Stilts for foraging and roosting...... 50 Figure 4.1: Proportion of nests constructed with different materials ...... 61 Plate 4.1: Scratches on the ground to form slight depression for nesting on bare ground ...... 61 Plate 4.2: Nest under construction with old feathers as nesting material ...... 62 Plate 4.3: A nest constructed with a variety of materials (mud chips, twigs, feathers and other random materials)...... 62 Plate 4.4: Black-winged stilt nest with three eggs. (Eggs laid in depression in the ground and surrounded by twigs, pieces of crab exoskeleton, feathers and dried mud chips) ...... 62 Figure 4.2: Boxplots of the distances of nests to road at the various Breeding Sites. Site RELU is relatively undisturbed, Site REMD is relatively most disturbed and Site REMU is most undisturbed 64 Figure 4.3: Boxplots of the distances of nests to closest neighbor at various breeding sites. Site RELU is relatively undisturbed, Site REMD is relatively most disturbed and Site REMU is most undisturbed...... 64 Plate 4.5: Black-winged stilt dropping on researcher ...... 68 Figure 4.4: Minimum permissible distance by Nest site. (Site RELU is relatively undisturbed, Site REMD is relatively most disturbed and Site REMU is most undisturbed)...... 69 Figure 4.5: Influence of clutch size on Minimum Permissible Distance ...... 69 Plate 4.6: Clutch size of 1 egg ...... 70 Plate 4.7: Clutch size of 2 eggs ...... 70 Figure 4.6: Frequency distribution of clutch size in Black-winged Stilt ...... 70 Figure 4.7: Cumulative frequency distribution of Black-winged Stilt incubation periods ...... 71 Plate 4.11: Breeding pair escorting hatchling away from the site. (One parent leading the chick while the other exhibits aggressive behavior)...... 77 Figure 4.8: Histogram showing frequency distribution of egg weights ...... 80 Figure 4.9: Histogram showing distribution of egg height ...... 80 Figure 4.10: Histogram showing frequency distribution of egg widths ...... 80 Figure 4.11: Relationship between position of egg in terms of order they were laid and egg height ... 80 Figure 4.12: Relationship between position of egg in terms of order they were laid and egg weight .. 80 Figure 4.13: Relationship between position of egg in terms of order they were laid and egg width .... 80 Figure 4.14: Boxplots of egg widths at the different breeding sites ...... 82 Figure 4.15: Correlation between egg weight and egg width ...... 83 Figure 4.16: Correlation between egg weight and egg height...... 83 Figure 4.17: Correlation between egg height and egg width ...... 84 Plate 4.12: Dog tracks found at nesting area ...... 87 Plate 4.13: Dog scat found near nesting area ...... 87 Plate 4.14: Broken Black-winged Stilt egg with spilled content ...... 87 Plate 4.15: Egg washed from nest due to flooding...... 87 Plate 4.16: Nest and egg covered by mud from crab hole ...... 87 Plate 4.17: Drowned Black-winged Stilt chick ...... 87 Figure 4.18: Percentage of time spent on activity groups ...... 88

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Figure 4.19: Diurnal time-activity budget of the Black-winged stilt ...... 88 Figure 4.20: Variations in the diurnal activity patterns of Black-winged stilts in the months studied . 90 Figure 4.21: Activity budget of Black-winged Stilts during the Breeding period ...... 90 Figure 4.22: Variations in diurnal activity patterns of Black-winged stilts at various study sites ...... 91 Plate 4.18: Foraging Black-winged Stilt with prey item between bill...... 92 Figure 4.23: Proportion of Macroinvertebrates sampled that occurred within the top 5cm and bottom 10cm. (This is based on densities calculated per m3 from the numbers of items collected during sampling)...... 93 Plate 4.19: Black-winged Stilts in a mixed flock with some other birds ...... 94 Figure 4.24: Nearest neighbour distance of foraging Black-winged Stilts to Conspecifics at the foraging sites ...... 95 Figure 4.25: Nearest neighbour distance of foraging Black-winged Stilts to other species among the foraging sites ...... 95 Figure 4.26: Depths in which Black-winged Stilts foraged at the foraging sites. (Number of observations = 59) ...... 96 Figure 4.27: Depth of water in which juvenile and adult Black-winged Stilts foraged ...... 96 Figure 4.28: Frequency of use of feeding styles...... 97 Figure 4.29: Boxplots of probing rates across the three foraging sites...... 98 Figure 4.30: Boxplots of Scything rates at the three sites ...... 98 Figure 4.31: Boxplots of Filtering rates at the three sites...... 99 Figure 4.32: Boxplots of Plunging rate at the three foraging sites...... 99 Figure 4.33: Boxplots of Intake rates across the three foraging sites ...... 100

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LIST OF TABLES

Table 4.1. Number of nests, total number of eggs laid, eggs hatched and mean number of eggs hatched per clutch size...... 72

Table 4.2. Nest status by clutch size (Total number of eggs in brackets) ...... 73

Table 4.3: Nest status at the sites for individual years ...... 74

Table 4.4: Factors influencing hatching success ...... 74

Table 4.5: Summary of egg measurements ...... 78

Table 4.6: Summary of egg measurements by order of laying ...... 79

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ABSTRACT

The Black-winged Stilt (Himantopus himantopus) is one of few waterbird species that breeds in wetlands on the coast of Ghana. In recent times, its population has seen an increase on

Ghana’s coast while other species are declining. The overall aim of the study was to investigate and document the breeding and foraging ecology of the Black winged Stilt in Ghana. The breeding ecology, diurnal time-activity budget and foraging behaviour of Black-winged Stilts were studied at the Densu Delta Ramsar Site (DDRS). Data were obtained through direct field observations, benthos sampling and video recordings of foraging Black-winged Stilts. Nests were monitored carefully to avoid trampling. A total of 845 eggs from 277 nests were monitored during two breeding seasons. The breeding season in 2016 started in early March and ended in late July, while that of 2017 was from early April till late July. Forty-nine percent

(49%) and 59% of nests were successful in 2016 and 2017 respectively. Clutch size ranged from 1-5 eggs and mean incubation period was 23.48 ± 2.88 days. Clutch size was the most important factor influencing nest success and egg hatchability, which suggests that the amount of investment in a nest (number of eggs laid) determines whether or not it will be abandoned.

Black-winged Stilts employed aggregation and aggressive displays to ward off predators and chase off other waders in fierce attacks during the peak hatching period. The greatest threats to breeding Black-winged Stilts on the Ghana coast are flooding of nesting sites and egg predation by wandering dogs. Macroinvertebrates in the benthos samples consisted mainly of polychaetes

(99%) which occurred at densities ranging from 138 to 1938 individuals /m2. About 86% of all macroinvertebrates in the benthic samples were found in the top 5 cm substrate depth. Black- winged Stilts fed by pecking, probing, plunging, scything and filtering. Plunging was the most frequently used feeding technique, accounting for 39.0% of all observations, whereas filtering was the least foraging method used accounting for only 1.0% of all observed foraging methods.

Pecking (x2=10.743, df=2, p-value=0.0046) and plunging (x2=8.7861, df=2, p-value=0.012)

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rates differed between the sites, however probing, scything and filtering rates showed no significant difference (p-value > 0.05). Black-winged Stilts spend an estimated 51% of the day time foraging, with 32% successful foraging attempts which varied across the three sites (x2=

27.086, df = 2, p-value = < 0.0001). Foraging site and age influenced foraging rate, while only site influenced intake rate. The findings of this study provide information on the breeding success and foraging behavior of Black-winged Stilt at Densu Delta Ramsar Site. Follow up studies should focus on the link between environmental parameters, prey type and availability, and the population densities of the Black-winged Stilts on the Ghana coast.

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CHAPTER ONE

1.0 INTRODUCTION

1.1 BACKGROUND

Ghana lies along the East-Atlantic and the Mediterranean flyways (Ntiamoa-Baidu, 1991b;

Ntiamoa-Baidu & Hepbum, 1988; Smit & Piersma, 1994) and receives migrant waterbirds that either spend winter on its coast or just rest a while to replenish energy stores before heading further south (Reneerkens et al., 2009). Ghana has over a 100 wetlands along its 550 km stretch of coast out of which five are designated as Ramsar sites under the Ramsar convention

(Ramsar, 2015). The rest, though not formally managed, have some forms of management under traditional systems (Gbogbo, 2007b).

Management systems on many of the non-protected wetlands have not been effective in past years due to influx of western cultural practices and corresponding neglect of traditional practices, increasing human population and dependence on wetland resources (Kondra, 2016).

Due to western culture and foreign religions such as Christianity and Islam, local community members do not subscribe to traditional systems of worship that established taboos and restrictions that govern the use of wetland resources. As a result, these individuals use the wetlands without regard for observing taboos and sacred days and traditionally instituted close seasons. People from different cultures and ethnicities have also migrated from their communities and settled around wetlands. These people do not submit to the existing cultures of the native settlers around the wetland and thus engage in practices that degrade the wetland.

Increasing human population also has put a strain on wetlands by way of land reclamation for settlements and extensive use of resources such as harvesting of mangroves and overfishing

(Kondra, 2016). Gordon et al. (1998) declared some of these unmanaged wetlands such as

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Korle, Chemu, Teshie and Kpeshie, Fosu and Benya lagoons as polluted and unable to support life. Attuquayefio & Gbogbo (2001) have also reported indiscriminate fishing, hunting, and harvesting of mangroves on these unmanaged wetlands.

A number of coastal wetlands along the coast of Ghana have been reported to support internationally important numbers of migratory waterbirds (Grimes, 1969; Ntiamoa-Baidu,

1991b; Ntiamoa-Baidu & Grieve, 1987; Ntiamoa-Baidu & Hollis, 1988; Theunis Piersma &

Ntiamoa-Baidu, 1995). The importance of these wetlands as staging areas and non-breeding grounds are also well established through long-term monitoring and demographic studies of waterbirds (Ntiamoa-Baidu, 1991b; Ntiamoa-Baidu & Hepbum, 1988). The importance of coastal wetlands in Ghana as habitats for resident and migratory waterbirds is also very well documented (Ntiamoa-Baidu, 1988, 1991b; Ntiamoa-Baidu & Hepbum, 1988; Ntiamoa-Baidu,

Nyame, & Nuoh, 2000).

Migrant waterbirds begin arriving on the Ghana coast from the end of August to early

September and some remain until April (Ntiamoa-Baidu et al., 1998) with peak counts observed between September and December. There is another peak count observed between

January and March during the northern spring migration (Ntiamoa-Baidu et al., 2014).

Waterbird populations are declining both globally (Rolet, Spilmont, Davoult, Goberville, &

Luczak, 2015) and locally along the Ghana coast (Gbogbo & Attuquayefio, 2010; Lamptey &

Ofori-Danson, 2014; Ntiamoa-Baidu, et al. , 2015). These declines have been attributed to climate change and anthropogenic activities; loss of wetland habitat to land reclamation for settlements, the ongoing coastal urbanization that has amplified the modification of their habitat in rate and magnitude, pollution of wetland water systems and degradation (Rolet et al.,

2015). Overfishing may have also depleted fish stocks (Kondra, 2016) that serve as food for some waterbirds, thus forcing these birds to seek alternative habitats. However, some species

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such as the Black-winged Stilt and curlew sandpiper have an increasing local population

(Ntiamoa-Baidu et al., 2015).

Habitat quality plays a major role in influencing the fitness and survival of waterbirds at both breeding and non-breeding locations. Hall et al. (1997) mention that habitat quality is used to refer to “the ability of an environment to provide conditions appropriate for the individual and the population persistence” and indicate that the term should be considered a continuous variable with levels from low to medium to high depending on the available resources that enable survival. Selection of wetland habitats by migrant waterbirds during the non-breeding season is influenced by availability of food, safe roosting sites and extent of disturbance (van

Eerden, 1984; Ens et al., 1990; Ens et al.,1994; Piersma, 1994; Hochbaum, 1995). Safety at breeding sites is also known to influence choice of wetland habitat for breeding birds (Burger

& Shisler, 1978; Goutner, 1990; Quintana & Yorio, 2018).

Many of the species of waterbirds that use Ghana’s coast are migratory, however some species are resident and breed in Ghana. For some species, part of the population is resident and the other part migrates to breed in temperate areas. Nevertheless, not all individuals of a species that skip migration breed locally. Some individuals are sometimes unable to meet their energy requirements to make the flight to the breeding areas and therefore have to skip migration

(Reneerkens et al., 2009). Fitness constraints can also make some individuals skip migration.

Age is another factor that can make an individual skip migration; some juvenile birds remain on the non-breeding grounds in their first year (Johnson et al., 2010).

Among the species known to breed in Ghana are the Little Tern (Sterna albifrons), the Collared

Pratincole (Glareoloa pratincola), and the Black-winged Stilt (Himantopus himantopus).

These species have been observed to breed at the DDRS and other coastal wetland sites. They

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are usually found nesting on sandy dunes within the wetland and sometimes nest together in loose colonies (personal observation).

Breeding success is a major factor controlling population dynamics of waterbirds species (Potts et al. , 1980; Rolet et al., 2015). With the exception of immigration, reproduction is the only way a population increases in number by having new members. Death and emigration result in population decrease. Holding immigration and emigration constant, population increase or decrease depends on births and deaths (Johnson et al., 2010). A balance between these factors ensures persistence of the species or population (Johnson et al., 2010). However, for a population to experience an increase, the birth rate should be higher than the mortality rate.

One key factor that determines the success of reproduction and the fitness and viability of new recruits is the diet of parents (Both, 2010). The food available for new recruits in a particular site also influences their growth rate and determines how many recruits will survive to adulthood to. These two factors are dependent on the quality of the habitat to possess characteristics that would provide required conditions for the individual and the population to persist.

Using the black-winged stilt as a focal species, this study focused on two important factors

that influence population dynamics of waterbirds; foraging and breeding.

1.2 Justification

Scientific studies in Ghana on shorebird foraging ecology have focused mainly on species assemblages and not on individual species (Battley et al., 2003; Gbogbo et al, 2009; Ntiamoa-

Baidu, 1991b; Ntiamoa-Baidu et al., 2000). Thus, there is very little work done on the foraging ecology of individual species in Ghana. Few studies have however focused on aspects of the foraging ecology of some species (Ahulu et al., 2006; Grond et al. , 2015).

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Shorebirds have low reproductive success, high juvenile mortality and delayed sexual maturity but high adult survivorship (Johnson et al., 2010). This phenomenon results in declining populations when death rate is higher than recruitment rate. Some species show declining populations while others are increasing (van Roomen et al., 2014; Rolet et al., 2015; IUCN,

2018). It is therefore important to investigate the factors driving the dynamics of the population trends. The resulting information will inform management interventions for species with declining populations.

The Black-winged stilt has an increasing population worldwide (IUCN, 2018) and is one of the common wader species in Ghana and has been recorded at several coastal wetlands in Ghana

(Ntiamoa-Baidu, 1991b). According to Ntiamoa-Baidu & Grieve (1987), Ghana is

“particularly important for the Black-winged stilt”. The Black-winged stilt is one of few wader species observed to breed in Ghana, however, various ecological aspects such as feeding and nesting behavior of the bird are yet to be fully understood.

Ntiamoa-Baidu et al. (1998) describes the feeding behavior and strategies employed by waterbirds in two coastal wetlands in Ghana and categorize the Black-winged Stilt as a pelagic- foraging wader. The foraging behavior and diet of Black-winged Stilt have been studied at various locations (Dias, 2017; Perez-Hurtado et al. , 1997; Ueng et al. , 2009).

The breeding ecology of the Black-winged Stilt has been studied in Europe (Cuervo, 2003,

2010a, 2010b; Tinarelli, 1991; Yeates, 1938), and the Middle East (Ashoori, 2011; Barati et al.

, 2012a). Rais et al. (2010) have also reported breeding Black-winged Stilt in Kallar Kahar

Lake district in Chakwal. According to Cuervo (2003) nest building is done by males and both sexes take turns in brooding the eggs. The females lay between 1 to 5 eggs; the eggs hatch mainly in June and the chicks leave the nest soon after hatching and feed on their own (Cuervo,

2003).

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Investigating the ecology of the Black-winged stilt to understand what drivers influence it is very important at this time when many waterbird populations are declining and waterbird habitats are being degraded. This would answer some of the questions raised by the increasing population of the species in Ghana. Both the breeding and foraging ecology of the Black- winged stilt have been studied intensively in other countries in relation to population increases and decreases for breeding and non-breeding periods (Figuerola, 2007) but very little work has been done in Ghana and other tropical countries. This study seeks to fill the knowledge gap and provide additional information on the factors that drive the ecology of the Black-winged stilt with respect to its foraging behavior and reproduction.

1.3. Research concept and key research questions

In the last decade, the global populations of waterbirds have been observed to be declining much to the dismay of waterbird researchers, conservationists and enthusiasts. Habitat loss has been indicted as the most important factor influencing this decline. Some studies have also attributed the declines to changing climatic conditions (Figuerola, 2007; Rolet et al., 2015) that affect patterns of food availability (Pearse et al. , 2013). The situation is not very different in

Ghana. However, there is not much information to explain the population declines at the species level. At the arctic breeding areas, several studies have been carried out to document nesting behavior and success as well as potential threats to young ones and as adult population as a whole ( Lindström & Agrell, 1999; Koivula et al., 2008; Bruinzeel et al. , 2010; Cooch,

2010; Hansen et al. , 2011; Berg, 2018). Studying the foraging patterns, diet and intake rate of the Black-winged Stilt before breeding, during breeding and post breeding, and documenting the reproductive success of the species in relation to prevailing threats and changing habitat conditions will provide further understanding on the population dynamics of the species.

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In view of these, the following objectives and hypothetical statements were made for this study:

1.4 Objectives

Main objective

To describe the breeding and foraging ecology of the Black winged stilt in Ghana using the

Densu Delta Ramsar wetland as a case study site.

Specific objectives

1. To describe breeding behavior and measure nest success of Black-winged Stilts in Ghana.

2. To describe diurnal time-activity budget of Black-winged Stilts in Ghana.

3. To describe foraging behavior and measure foraging rate of Black-winged Stilts in Ghana.

Hypothesis

The following hypotheses were investigated in the study:

1. Presence of water is a factor for selecting breeding site.

2. Presence of vegetation influences breeding site selection.

3. Proximity to road network affects nest site selection and nest success of breeding

Black-winged Stilts.

4. Black-winged Silts spend majority of their time foraging.

5. Foraging style and rate are influenced by water depth.

6. Foraging rate changes with time of day.

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CHAPTER TWO

2.0. Literature review

2.1 Wetlands

A habitat is the natural environment of an organism or simply put, where an organism lives.

Habitats are usually classified under two thematic groups, terrestrial and aquatic. A third classification which usually is a subset of terrestrial is arboreal habitat. Some habitats are however halfway between terrestrial and aquatic systems. These are broadly grouped under the term wetlands. Wetlands are usually adjacent terrestrial systems and lead into aquatic systems

(Cowardin et al., 1979; Mitsch & Gosselink, 2015; Wagner, 2004). They have been described as “a halfway world between terrestrial and aquatic ecosystems, exhibiting some of the characteristics of each system” (Mitsch & Gosselink, 2015). Wetlands have numerous distinctive features, the most obvious being “the presence of standing water for some period of the year, unique soil conditions, and organisms, especially vegetation, adapted to or tolerant of saturated soils” (Mitsch & Gosselink, 2015).

Wetlands have the ability to support distinctive flora and fauna components and have been classified as unique ecosystems on their own; unique in the sense that they have features and characteristics that no other habitat possesses (Harisha et al., 2011; Mitsch & Gosselink, 2015;

O’Keefe et al., 2000). The hydrophilic soils of wetlands is a distinguishing feature that separates wetlands from other water bodies- and are usually inundated most times of the year if not perpetually, as (Mitsch & Gosselink, 2015) indicate, wetlands can range from “small prairie potholes of a few hectares in size to large expanses of wetlands several hundreds of square kilometers in area”.

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Wetlands are difficult to define due to the wide variety of types and forms, according to (Mitsch

& Gosselink, 2015) these three features run through wetland definitions and wetland types and can be used to easily identify a wetland:

1. Wetlands are distinguished by the presence of water, either at the surface or within the root zone.

2. Wetlands often have unique soil conditions that differ from adjacent uplands.

3. Wetlands support biota such as vegetation adapted to the wet conditions (hydrophytes) and, conversely, are characterized by an absence of flooding-intolerant biota.

Mitsch & Gosselink (2015) explain that although the above features and definitional components are straightforward, they do not necessarily facilitate the formation of a single solve-all definition due to the following six characteristics that set wetlands apart from other ecosystems;

1. Although water is present for at least part of the time, the depth and duration of flooding vary considerably from wetland to wetland and from year to year. Some wetlands are continually flooded, whereas others are flooded only briefly at the surface or even just below the surface. Similarly, because fluctuating water levels can vary from season to season and year to year in the same wetland type, the boundaries of wetlands cannot always be determined by the presence of water at any one time.

2. Wetlands are often located at the margins between deep water and terrestrial uplands and are influenced by both systems. This ecotone position has been suggested by some as evidence that wetlands are mere extensions of either the terrestrial or the aquatic ecosystems or both and have no separate identity.

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3. Wetland species (plants, animals, and microbes) range from those that have adapted to live in either wet or dry conditions (facultative), which makes difficult their use as wetland indicators, to those adapted to only a wet environment (obligate).

4. Wetlands vary widely in size, ranging from small prairie potholes of a few hectares in size to large expanses of wetlands several hundreds of square kilometers in area. Although this range in scale is not unique to wetlands, the question of scale is important for their conservation.

Wetlands can be lost in large parcels or, more commonly, one small piece at a time in a process called cumulative loss. Are wetlands better defined functionally on a large scale or in small parcels?

5. Wetland location can vary greatly, from inland to coastal wetlands and from rural to urban regions. Whereas most ecosystem types—for example, forests or lakes—have similar ecosystem structure and function, there are great differences among different wetland types such as coastal salt marshes, inland pothole marshes, and forested bottomland hardwoods.

6. Wetland condition, or the degree to which a wetland has been modified by humans, varies greatly from region to region and from wetland to wetland. In rural areas, wetlands are likely to be associated with farmlands, whereas wetlands in urban areas are often subjected to the impact of extreme pollution and altered hydrology associated with housing, feeding, and transporting a large population. Many wetlands can easily be drained and turned into dry lands by human intervention; similarly, altered hydrology or increased runoff can cause wetlands to develop where they were not found before.

They also vary in type and their classification can be on the basis of location, form and origin: there are inland wetlands and coastal wetlands; riverine, palustrine, lacustrine, estuarine and marine; and natural and man-made wetlands (Cowardin et al., 1979; Miller, 2004; Mitsch &

Gosselink, 2015).

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The Ramsar Convention, the inter-governmental treaty for the conservation of wetlands defines wetlands as “areas of marsh, fen, peat land or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt including areas of marine water, the depth of which at low tide does not exceed six metres” (Ramsar Convention, 1998).

Wetlands play numerous roles in the ecosystem; including but not limited to groundwater purification, run-off water retention, flood prevention, shoreline stabilization and habitat for waterfowl and other fauna (Mitsch & Gosselink, 2015; O’Keefe et al., 2000). These roles have both direct and indirect influences on human populations around them in the same way human activities also influence the health of the wetlands and in effect how effectively these roles are played. Wetlands, as stated by (Mitsch & Gosselink, 2015) have been called “nature’s supermarkets because of the extensive food chain and rich biodiversity that they support”. They have been known to play major ecological roles in the landscape by providing “unique habitats” for a wide variety of plants and animals (Mitsch & Gosselink, 2015). With the onset of current concerns about the health of the planet, wetlands are being described by some as important carbon sinks and climate stabilizers on a global scale (Kennedy & Mayer, 2002; Mitsch &

Gosselink, 2015). Kennedy & Mayer, (2002) point out that “due to high productivity and low decomposition rates, wetlands, particularly peat lands, sequester an enormous volume of carbon”. They also argue that although “wetlands occupy only about 6% of the world’s land surface, they contain 14% of the terrestrial biosphere carbon pool” (Kennedy & Mayer, 2002).

Wetlands have also been described as the kidneys of the landscape due to the functions they play as downstream receivers of water and waste from both natural and human sources (Mitsch

& Gosselink, 2000; 2015). They mitigate both floods and drought by stabilizing water supplies much as sponges soak water (Mitsch & Gosselink, 2015).

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It is however troubling to reflect that for many years people regarded wetlands as waste lands with little value to humans which led many to drain them or use them as refuse dumps (Notes,

1998; O’Keefe et al., 2000).

“Wetlands are among the most important ecosystems on earth” (Mitsch & Gosselink, 2015).

The importance of wetlands cannot be overlooked in present times with increasing knowledge about their ecological and economic functions and significance (O’Keefe et al., 2000). Their value for fish and wildlife have been known for centuries but as (Mitsch & Gosselink, 2015) point out, other values and benefits have only been recently identified. Our knowledge of wetland although as vast as never before in history is still limited in many ways. With current industrialization, wetlands are being polluted beyond repair. With the destruction of wetlands, wetland functions such as groundwater purification would not be performed and our groundwater would soon be beyond use. Groundwater (aquifers) feeds wells and lakes providing clean usable water for agricultural and domestic use (Ramsar Convention, 1998).

Wetlands also feed river systems and streams with clean water by trapping runoff from towns and cities and filtering it before it moves into rivers, lakes and streams (Kennedy & Mayer,

2002; Mitsch & Gosselink, 2015; World Wildlife Fund Canada, 2015). Another function of wetlands is the prevention or reduction of erosion, this it does by trapping running water and releasing it in small quantities at slow paces, thus reducing the eroding effect of the otherwise fast moving volumes of water (Ramsar Convention, 1998). A study conducted in the USA estimates that “0.4 hectares of wetland can store over 6,000 cubic metres of floodwater”

(Ramsar Convention, 1998).

Aside the ecological benefits derived from wetlands, wetlands provide economic benefits and means of sustaining communities that live around and within them (Janssen et al., 2005; Mitsch

& Gosselink, 2015).

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The Wetlands of Ghana form an ecologically valuable resource providing feeding, roosting and nesting sites for thousands of migratory and resident birds; marine turtles; many species of fish; plant genetic materials for research; and a major source of income for especially poor communities (Anku, 2006; Ntiamoa-Baidu, 1988, 1991a; Ntiamoa-Baidu et al., 1998).

2.2. Wetland fauna and flora

Wetlands possess different microhabitat structures that both generalist and specialist species can exploit for resources such as space and food. Waterbirds, defined as “species of birds that are ecologically dependent upon wetlands” (Rose & Scott, 1997) are a usual sight at many wetlands. Several species of waterbirds visit the coast of Ghana, some of the notable species recorded are the Sanderlings (Calidris alba), Common Sandpiper (Actitis hypoleucos), Ringed plover (Charadrius hiaticula), Bar-tailed Godwit (Limosa laponica), Knot (Calidric canutus),

Grey plover (Pluvialis squatarola), Wood sandpiper (Tringa glareola), Spotted Redshank

(Tringa erythropus), Little Stint (Calidris minuta), Curlew Sandpiper (Calidris ferruginea),

Black-winged Stilt (Himantopus himantopus) among others (see Ntiamoa-Baidu & Gordon,

1991 for complete list of waterbirds at all five Ramsar sites).

Small mammal which comprise the orders Rodentia, Chiroptera and Insectivora have been recorded at various wetlands. A study by Attuquayefio & Ryan (2009) revealed a total of 11 species of small mammals were recorded at Muni-Pomadze, comprising 47 individuals of seven rodent species, four individuals of two insectivore species and two individuals of two bat species while four species were recorded at Keta, made up of three individuals of two species of insectivores and eight individuals of two rodent species.

Some wetlands which are associated with lagoonal or riverine systems hold important fish stocks. For instance in the case of the Densu Delta wetland, Tilapia zilli and Sarotherodon

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melanotheron have been documented to be the most abundant species (Ntiamoa-Baidu &

Gordon, 1991).

Wetlands serve as habitat for invertebrates such as crabs (Ntiamoa-Baidu & Gordon, 1991).

Benthic organisms are an important component of wetland biomass; several species of polychaetes serve as prey for other wetland fauna and have been used as biological indicators of changes in the environment especially estuarine systems (Tomiyama et al., 2008).

Wetland plants include not only plants that are able to withstand continual wet conditions but also those that can survive seasonal dry conditions (Kennedy & Mayer, 2002; Mitsch &

Gosselink, 2015). Sessuvium portulacastrum is a typical plant found in almost all coastal wetlands along the coast of Ghana (Ntiamoa-Baidu & Gordon, 1991). Ntiamoa-Baidu &

Gordon (1991) provide a comprehensive list of floral components of the five protected coastal wetlands in Ghana.

2.3. Wetland degradation

Mitsch & Gosselink (2015) indicate how wetlands are only valuable when they provide direct benefits to humans; they state this as the reason why wetlands are often legally protected whereas they weren’t in the past. They also provide a historical overview of the importance of wetlands to humans and settlements.

Wetlands in the past were regarded as wastelands and linked to the propagation of mosquitoes and malaria, thus were avoided (O’Keefe et al., 2000). This caused many people to fill them up because their uses and importance was not previously known and understood. Other people not knowing the importance and uses of wetlands have filled them up to create land space for development of settlements and other infrastructure or for agricultural establishments (Kondra,

2016). Although wetlands serve as sinks to remove dissolved waste materials from running water before they finally enter both surface and underground water systems, they have limits

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to their functionality and the amount of waste they can remove in space and time (O’Keefe et al., 2000; World Wildlife Fund Canada, 2015).

Many wetlands are degraded both in space and in quality making them unable to perform their filtration functions effectively. Land reclamations have drastically reduced the natural land surface covered by wetlands (Kondra, 2016). This reduction has consequences for water purification, flood retention and shore line protection because of the resultant reduction in the volume of water that the wetland can hold at any given time (O’Keefe et al., 2000; World

Wildlife Fund Canada, 2015). Settlements and industries around wetlands release untreated sewage into them greatly increasing pollution in the water and nutrient load. This has implications for the overall quality of the water, the physical as well as the biological components of the wetland. Degradation also disrupts the natural scenic beauty of the wetland

(O’Keefe et al., 2000) and in some cases causes eutrophication that reduces the oxygen content of the water and consequently reduces fish stock. The chemicals from the sewage also have implications for benthic communities, greatly reducing their numbers and consequently affecting organisms of other trophic levels that rely on them for food (Tomiyama et al., 2008).

2.4. The Ramsar Convention

The Convention on Wetlands (Ramsar, 1971) also called the "Ramsar Convention" – is an intergovernmental treaty that embodies the commitments of its member countries to maintain the ecological character of their Wetlands of International Importance and to plan for the "wise use", or sustainable use, of all of the wetlands in their territories”. The Convention which is named after the city of Ramsar in Iran, where the Convention was signed in 1971 outlines nine

(9) criteria for use in designating a site as a Ramsar site. Under the convention, contracting parties are obligated to select suitable wetlands in their countries that meet the criteria for designation as wetlands of international importance. The Convention also states that wetlands

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should be listed according to their ‘international significance in terms of ecology, botany, zoology, limnology or hydrology’ (Finlayson et al., 2000).

The mission of the convention is “the conservation and wise use of all wetlands through local and national actions and international cooperation, as a contribution towards achieving sustainable development throughout the world”. The convention operates under three pillars and requires contracting parties commit to: (i) “work towards the wise use of all their wetlands”

(not just those under the convention), (ii) “designate suitable wetlands for the list of wetlands of international importance and ensure their effective management” and (iii) “cooperate internationally on transboundary wetlands, shared wetland systems and shared species” (The

Ramsar Convention Secretariate, 2018).

For effective management and conservation purposes, the Convention also obligates member countries to monitor these wetlands to determine. ‘… if the ecological character of any wetland in their territory included in the List has changed, is changing, or is likely to change as the result of technological developments, pollution or other human interference’ (Finlayson et al.,

2000). Waterbirds species richness, abundance and diversity have potential for used as biological indicators of the overall health of a wetland due to their high sensitivity to changes in the environment (Battley et al., 2003; Ntiamoa-Baidu & Gordon, 1991).

Ghana joined the Ramsar Convention on Wetlands in 1988 (Ntiamoa-Baidu & Gordon, 1991).

Five coastal wetlands were designated as Ramsar sites in 1992. According to Ntiamoa-Baidu

& Gordon (1991) these wetlands are situated in very densely populated areas and subject to intensive resource exploitation.

Willoughby et al. (2001) point out the importance of noting that the wetlands obtained the status as a Ramsar site only due to the protection of the Palearctic bird population that migrate

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there during the northern winter. In effect, the ability to support important populations of waterbirds along the flyway is what confers importance to the wetland.

2.5. Breeding ecology

2.5.1. Breeding behavior

Changes in Black-winged Stilt population size are related to changes in philopatry and increases in dispersal beyond the traditional range of the species (Figuerola, 2007). The results from Figuerola (2007) indicate that climatic conditions influence the dispersive behaviour of individual birds.

Northern populations of Black-winged Stilts make long-distance migratory movements, travelling southwards to their wintering grounds between August and November and returning to their breeding areas between March and April (Hayman et al., 1987). In more temperate regions the species is sedentary or only locally dispersive (del Hayo et al., 1996). Black-winged

Stilts breed solitarily or in loose colonies of 2-50 or occasionally up to several hundred pairs

(del Hayo et al., 1996). It is typically a gregarious species, occurring in small groups (Snow &

Perrins, 1998) (up to 15 individuals) (del Hayo et al., 1996) or larger flocks of several hundred up to a thousand individuals on migration, during the winter (Snow & Perrins, 1998).

2.5.2. Mate selection and copulation

Different groups and species of birds exhibit a wide range of behavior when it comes to mate selection and mating. Goriup (1982) reports that Black-winged Stilts form stable pairs which are maintained throughout the breeding period and sexual behavior only took place between couples. Goriup (1982) indicates that they did not perform elaborate pairing rituals and that pairing was demonstrated by sharing a feeding area.

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Goriup (1982, pg. 19) documents copulation behavior for the Black-winged stilt. He provides details of his observations on the pre- and post-copulatory displays as follows:

“All observed copulations took place in water, which seemed necessary for success (probably owing to the bill-dipping sequence by the male). Two attempts on land failed well before mounting would have occurred. On the four successful occasions, the female always initiated the ceremony, usually by adopting her characteristic inclined posture as the male walked past. Once, on land, a female pecked at the male's bill as though picking at a shared food item, and then led him into shallow water, where mating took place. As soon as the female assumed the copulation posture, which was held rigidly throughout, the male became very excited, puffing out his feathers to appear much larger than his mate, and striding in semicircles from one side of her to the other, always passing behind. Each time that he came up to her shoulder, he paused to bill- dip and preen his breast or underwing. This cycle was repeated two to five times, ending when the male adopted an erect posture prior to mounting). To achieve cloacal contact, the male flexed his legs so that the whole length of the tarsi rested on the female's back; balance was maintained by wing-flapping. After dismounting, both male and female adopted upright postures and performed the bills-crossed ceremony: standing close to the female, the male crossed his bill over hers and extended his wing over her back; in this pose, both walked about a metre, either directly forward or in a shallow arc, before separating. The male generally then resumed feeding immediately, while the female stood or preened for some seconds before commencing to feed herself. The whole procedure lasted about one minute.”

2.5.3. Site selection

Black-winged Stilts typically breed in “shallow freshwater and brackish wetlands with sand, mud or clay substrates and open margins, islets or spits near water level” (Snow & Perrins,

1998). Suitable habitats include marshes and swamps, shallow lake edges, riverbeds, flooded fields (del Hayo et al., 1996), irrigated areas (Snow & Perrins, 1998), sewage ponds (del Hayo et al., 1996) and fish-ponds (Snow & Perrins, 1998). Black-winged Stilts may also breed around alkaline and high-altitude lakes (del Hayo et al., 1996) or in more saline environments such as river deltas, estuaries (Snow & Perrins, 1998), coastal lagoons (Johnsgard, 1981; Snow

& Perrins, 1998), and saltpans, coastal marshes (del Hayo et al., 1996) and swamps (Snow &

Perrins, 1998).

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Cuervo (2004) studied the nesting behavior and characteristics of a mixed colony on Black- winged stilt and pied avocets and indicate that Black-winged stilt were better adapted to nest close to water than the avocets. Ashoori, (2011) reports that after the construction of culture ponds in 2005 for sturgeon in 22 Bahman wetland, which destroyed nesting areas of Black- winged Stilts, Black-winged Stilts were not observed at the wetland between 2006-2010, although Black-winged Stilts were spotted visiting the site possibly scouting for potential breeding sites. Black-winged Stilts show a preference for open areas close to foraging sites with good all-round (360 degree) visibility (Johnsgard, 1981).

2.5.4. Black-winged Stilt Clutch size

Elmalki, et al. (2013) report the clutch size of Black-winged Stilts to be between 3-4 eggs.

They record egg length, width, volume and shape index of 43.98±0.16, 31.25±0.16, 21.96±0.22 and 71.15±0.47 respectively. Grant et al. (1999) recorded over 77% of all completed clutches containing four eggs. Cuervo (2005) recorded 79% occurrence of nests with 4 eggs, 19% for nests with 3 eggs and 2% for nests with 2 eggs.

Adamou et al. (2009) also report that most of the complete nests had 4 eggs with only 11 out of 285 nests containing 3 eggs. They also found that within a clutch, there is some variability; the last egg laid was usually smaller than the clutch mean. They also measured egg mass, length, breadth and volume and found that the measurements decreased from2004 to 2007, attributing these decreases to deteriorating hydrological conditions in the wetland. Ashoori

(2011) recorded one clutch containing 5 eggs and attributes the high occurrence of nests with

4 eggs and the single nest with 5 eggs to good food supply and habitat quality. A clutch size of four eggs has also been recorded for all of 12 nests in Shirinsu wetland in Iran by Gholami et

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al. (2017). They recorded egg length, width and weight to be 41.9±0.6mm (41 min and 43 max), 29mm and 12±0.07g (12-12.3) respectively for 48 eggs.

2.5.5. Parental care and incubation period

Parental care refers to the amount of resources invested by parents to ensure the survival of their offspring. Black-winged Stilts show parental care from protecting nests and egg to guarding chicks till fledging (Ashoori, 2011; Cuervo, 2003; Goriup, 1982; Narayana et al.,

2005). Chicks leave the nest soon after hatching and feed on their own(Cuervo, 2003). Parents have been observed leading their chicks out of the breeding area (Ashoori, 2011; Goriup, 1982).

Incubation of eggs in Black-winged Stilts is done by both sexes and commences after clutch completion (Cuervo, 2003; Cuervo, 2005; Yeates, 1938), and both parents invest equal amount of time and effort to nest attendance (Cuervo, 2003). Time spent at the nest during incubation was significantly larger in males that in females, however, females spent more time at the nest during egg laying so in total both invest similarly (Cuervo, 2003). Boekel (2012) also notes contrastingly that parental care was mainly carried out by the male and the female disappeared two weeks before the chick was fully grown. Also contrary to other literature, Boekel (2016) observed that incubation started and continued right the first egg was laid probably due to bad weather conditions.

Cuervo (2005) report a 22 day incubation period same as Toral & Figuerola (2012). Boekel

(2016) however, report an incubation period of 28 days and pledging period of 40 days.

2.5.6. Deterrent behavior

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Many species have mechanisms for protection; both plants and animals. Some plants have thorns to protect from predation while others appear unpalatable. Several mechanisms are employed for protection in the animal kingdom ranging from appearing poisonous to actively warding off attackers. Stilts (Recurvirostridae) have been observed to be aggressive in warding off predators especially during the breeding season (Ashoori, 2011; Pierce, 1986).

(Goriup, 1982) reports that “When a Black Kite flew over, the male performed the curious prancing display, the stilt adopted an upright posture, flapping his wings and prancing from one foot to the other for about ten seconds, until the kite was no longer overhead.” Narayanan

(2005) mentions that a Black-winged Stilt responded to their presence by calling and doing the

“broken-wing drama” to alert other Black-winged Stilts. The other Black-winged Stilts immediately took flight and circled the area making similar calls as the individual who raised the alarm. Ashoori, (2011) mentions that Black-winged Stilts defended their nests and small territories, behaving aggressively towards intruders, even humans. They posed as if they had a broken wing to distract the attention of the intruder from their nests and eggs. They even defended their nests and territories against other stilts, frequently a group of Black-winged

Stilts were observed attacking birds of prey such as the Marsh Harrier (Circus aeruginosus) and Eurasian Hobby (Falco subbuteo).

2.5.7. Egg shell removal and egg capping

Many birds have been reported to remove empty shells from their nests after eggs have hatched

(Nethersole-Thompson & Nethersole-Thompson, 1986; Skutch, 1976). Parmelee et al. (1968) report that the urge to remove empty shells from the nest in Stilt sandpipers (Calidris himantopus) is so strong that that they can be captured by baiting a trap with an empty shell.

This phenomenon has been observed in the breeding behavior of Black-winged stilt; which remove the shells of hatched eggs immediately after hatching (Sordahl, 1994; Tinbergen et al.,

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1962). Many explanations have been offered for this Phenomenon. Tinbergen et al., (1962) offers five hypotheses that seek to explain why birds remove empty shells from the nest: 1.

Externally cryptic eggshells have quite conspicuous white insides which might be a source of attraction for predators to visit the nest and prey on the chicks; 2. It also offers that the shell of a previously hatched egg can get attached to unhatched eggs and cause another phenomenon called egg capping. This creates an extra layer of shell that the hatchling must break through, however does not have the mechanism to and can get trapped in a double shell; 3. the empty shells are removed to prevent injury to the chicks from the sharp edges; 4. the organic material of the shell and the remnants of its content could promote growth of bacteria and mold in the nest; 5. Hatched shells could also interfere with brooding in the nest. Sordhal (1994) reports on his field observations and experiments on the eggshell removal behavior of American avocets

(Recurvirostra Americana) and the Black-necked stilt (Himantopus mexicanus) and concludes that hypothesis 1 (antipredatory) is most plausible.

2.5.8. Sources of nest failure

Nest failure in waterbirds has been attributed to predation by several authors (Barshep et al.,

2011; Bolton et al., 2007; Grant et al., 1999; Jackson, 2001; Koivula et al., 2008; Kosztolányi et al., 2009; Morgan et al., 2011). Predation can take many forms including consumption by other birds like crows (Bolton et al., 2007; Koivula et al., 2008); consumption by small rodents such as hedgehogs (Jackson, 2001) and rats (Cuervo, 2004), mammals such as foxes(Bolton et al., 2007), minks (Koivula et al., 2008), dogs (Kosztolányi et al., 2009); lizards (Kosztolányi et al., 2009) among others. Barshep et al. (2011) point out that predators such as the Arctic fox

(Alopex lagopus) prey primarily on lemmings (Lemmus sibiricus) but switch their diet to the shorebirds eggs and nests during years when rodent abundance is low.

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Pierce (2018) recounts that predation by mammals was responsible for 49% of nest failures in the Pied stilt and 64% in the Black stilt, even nests that were protected were preyed on. During his study, eggs were eaten by ferrets, ferel cats, Norway rats, harriers, stoats (Mustela erminea), weasels (Mustela nivalis) and hedgehogs (Ericaceus europaeus) and mammals were also observed taking chicks as well as eggs (Pierce, 2018). Factors observed to affect nest failure include nesting habitat, antipredator behavior, colonial or solitary nesting behavior, timing of and duration and duration of nesting, chick behavior, and fledging period (Pierce, 2018).

Colonial nesting is less likely to fail; there is high vigilance rate with more individuals on the lookout to detect intruders early (Pierce, 1986). Pierce (1986) observes that at Pied stilt colonies, the first individual to detect a predator quickly jumps into the air and raises an alarm.

Other individuals in the colony are quickly alerted to mobilize to attack the intruder or divert its focus from the nest using distracting displays. Pierce notes that Black stilts that are solitary, do not have this advantage of early detection and mob action. Spacing of nests is also mentioned to affect susceptibility to predation. Pierce postulates that wide spacing of Pied stilt nests is an antipredatory adaption; spacing is less likely to attract predators compared to aggregated nest yet nest were close enough to facilitate mob distractions. Solitary nesters however do not space out to reduce aggregation but as Pierce explains, rely on their own ability to detect and repel predators. Also, colonial nesters can repel multiple attacks whereas solitary nesters have no defense against multiple attacks.

With respect to timing and duration of nesting, Black stilts started nesting earlier than Pied stilts. Pierce observed that during the three years of study, no early nests of Black stilts were successful although one survived to hatching. He attributes this high predation rate to shortage of alternative sources of food. He noted that the Pied stilts had a low success rate earlier and later in the breeding season, explaining that late nesting birds also had deal with an increase in predator numbers; both adults and kittens as food became abundant. Earlier nests and late nests

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are more prone to predation than middle nests, thus species with longer nesting time are more susceptible to predation induced failure than species with shorter nesting period. also timing of nesting, if nesting period coincides with lean periods of food availability, there’ll be more predator threats, however if the timing falls within a period of high influx of adults and kittens, then predation is still high. Late breeding has also been attributed to nest success by (Barati et al, 2012a).

Pied stilt chicks fledged significantly earlier than Black stilts and had a higher survival rate

(Pierce, 2018). Pierce (2018) indicates that most Black stilt chick deaths occurred during the first fortnight of fledging and more disappeared later on and that chicks that have not fledged are more vulnerable due to limited escape options. A fledged chick without a guarding parent is less likely to be preyed on than a chick that has not fledged but has a guarding parent.

Whereas the fledged chick can fly away or even jump into the air going beyond the reach of the typical predator (mammals in this case), the unfledged chick can only run or swim but never faster than the predator (Pierce, 2018).

Trampling of nest by grazing cattle has been reported to be an important source of nest failure for many species of birds particularly waterbirds breeding in grasslands and farmlands

(Calladine et al., 2014). Waterbirds that breed in farmlands face another threat, movement of farm machinery during harvesting or cultivation can destroy an entire colony of nests and the eggs contained in them. Pierce (1986) states that stilts (Family: Recurvisrostridae) nest on the ground, an attribute that exposes them to predation by mammals. This is supported by introductory arguments made by Martin (1993) that ground-nesting birds suffer greater nest predation than off ground nesting birds.

2.5.9. Nest monitoring and predation or nest success

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Grant et al. (1999) in studying the Breeding success and causes of breeding failure of curlew Numenius arquata in Northern Ireland revealed that nest handling did not increase the chances of nest predation. They varied the monitoring intensity at various nests by handling the eggs in some nests to measure egg morphometrics after clutch completion while some nests were left untouched. They measured daily predation rates and found no significant difference between the two treatments showing that handling and measuring of eggs did not influence the likelihood of predation.

Hansen et al. (2011) tested the negative effects of egg floatation and handling on the hatchability of egg and found that floating the eggs and handling did not negatively affect egg hatchability. They however indicate that they follow best practices for nest monitoring and handling such as minimizing the time spent at the nest and using water within the tolerance limit of the eggs and quickly but gently dry off the eggs with paper towels before returning them back to the nest. The minimum time spent at the nest, according to them reduces the likelihood of leaving olfactory cues that may attract predators to the nest.

2.5.10. RUNT EEGGS

Eggs that are abnormally small are called runt eggs (Mallory et al., 2004; Mulvihill, 1987).

The occurrence of runt eggs is not a new phenomenon and has been sighted and recorded by egg collectors since 1800’s. The earliest report on runt eggs was by Jacobs (1898), however, prior to his documented report, many had encountered it but it was not documented. Mallory et al., (2004), reports that runt eggs occur in clutches of a wide variety of avian species. They report on their survey of waterfowl researchers to determine the “natural frequency of occurrence of runt eggs in wild nesting ducks, geese and swans”. Their study revealed 215 out of 551,632 (0.039%) eggs to be runt eggs. They indicate that “cavity nesting waterfowl had

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lower incidence of runt eggs that ground nesting waterfowl”. They mention that their results were consistent with the hypothesis that runt eggs result from a temporary impairment of the reproductive tract. And offered that the hypothesis possibly explains why runt eggs occur in all bird species studied. Mulvihill (1987), while examining nest boxes came across a runt egg in a nest with a clutch of 3 eggs belonging to the Eastern Bluebird (Sialia sialis); two eggs were later laid making it 5. The runt egg measured 11.0 x 9.0 mm and weighed 0.46g, while the other 4 eggs in the nest measured 22.0 x 17.0mm; 21.0 x 16.0mm; 22.0 x 16.5mm; 21.5 x

17.0mm with an average of 21.6 x 16.5. He reports that the egg weighed 16% less that the average weight of a bluebird egg.

2.6. Foraging ecology

2.6.1. Time budget

It has been recorded that waders including the Black-winged stilts spend majority of their time foraging. Nol et al., 2014 report that they spend between 20–85% of total time foraging. This feeding behavior exhibits temporal variations. Waterbirds exhibit different patterns of behavior at different times of the day, having foraging and resting peaks. Some birds however, forage throughout the day with short rest periods. They report that the amount of time spent foraging in inversely proportional to body size, thus smaller birds spend more time foraging compared to larger birds. This could be due to prey type and size. Smaller birds will feed rapidly and show little selection for food and will continue foraging the entire day with short breaks in between whereas larger birds spend more time searching for high quality prey items and have longer rest to digest ingested food, thus overall time spent feeding will be smaller than the smaller birds.

Ntiamoa-Baidu et al., (1998) reported this relationship between body size and guild and proportion of time spent foraging. They found that smaller birds significantly spent more time

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foraging and that species which spent the least proportion of daytime foraging included larger members of different guilds such as Grey plover, Curlew, Black-tailed godwit, Greenshank,

Avocet, Grey heron and White pelican. They report that species feeding on small prey spent a lot of time feeding than fish-eating species. According to them, species which spent the greatest proportion of the daytime foraging (over 75%) were Wood Sandpiper (Tringa glareola),

Kittlitz's Plover (Tringa glareola), Common Sandpiper (Actitis hypoleucos), Turnstone

(Arenaria interpres), Ringed Plover (Charadrius hiaticula)and White-fronted Plover

(Charadrius marginatus), all small sized birds belonging to guild 2 (the visual surface foragers) and feeding on small prey. Their study observed some species such as the avocet foraging during the night, contrasting with earlier studies by Zwarts et al., (1990) in Senegal.

2.6.2. Foraging behaviour

During of the breeding season Black-winged Stilts occupy the shores of large inland waterbodies and estuarine or coastal habitats (del Hayo et al., 1996) such as river deltas (Snow and Perrins 1998), coastal lagoons (Johnsgard 1981, Snow and Perrins 1998) and shallow freshwater or brackish pools with extensive areas of mudflats, salt meadows (Johnsgard 1981), saltpans, coastal marshes (del Hayo et al., 1996) and swamps (Snow and Perrins 1998) or simply just about anywhere they can obtain food and safe roosting areas. Goss-Custard et al.

(2006) state that wading bird that congregate outside the breeding season off the European coast must survive until spring by “avoiding death from starvation or from enemies”, and also

“accumulate sufficient reserves to reach their frequently distant breeding grounds in good condition”. Foraging thus play an important role in the fitness and survival of waders.

Foraging in simple terms is how an organism obtains its food from wild sources. Food availability, abundance, quality and accessibility are major drivers of population increase or

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decrease of species. Goss-Custard et al. (2006) explain that for an animal (wader) to survive, there must be a balance between the individual’s rate of energy expenditure and consumption where energy expenditure depends on “metabolic costs plus any other cost of thermoregulation at low temperatures”. Energy consumption on the other hand depends on the time available to the individual for feeding-the duration of the exposure period of the food patches-and on the intake rates while feeding which in turn, depends on the profitability of the prey as well as the individual’s susceptibility to interference. They further note that when daily energy consumption exceeds daily expenditure, individuals accumulate energy reserves or maintain them if a prior maximum level has been reached already but when daily requirements exceed daily consumption, individuals draw on energy reserves and when reserves drop to zero, there is starvation which may lead to death.

Researchers have attributed the declines in populations of waterbirds to changing climatic conditions (Figuerola, 2007; Rolet et al., 2015) and their effects on the patterns of food distribution and availability (Pearse et al., 2013). It only makes sense that animals will aggregate at areas of food abundance. Smith & Sweatman (1974) observe that “Birds often returned to previous capture sites and were more likely to do so when they found prey there quickly“ ( see Goss-Custard et al., 2006). Despite the risk of capture, they still visited the site because due to their previous experience of finding prey; there appears to be a tradeoff between safety and feeding. In such a case, the bird might respond by being extra vigilant which can reduce foraging efficiency. Foraging behavior is a complexity of many factors.

Ntiamoa-Baidu et al. (1998) studied water depth selection, daily feeding routines and diets of water birds found in two coastal lagoons in Ghana. They examined a total of 118,648 individuals of 36 different waterbird species belonging to 3199 flocks during October-

November 1994. The study revealed that feeding habitats ranged from dry to wet mudflats and shallow water of not more than 20 cm. Foraging birds exhibited a wide range of feeding styles

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using visual and/or tactile means for detecting prey; pecking, probing, stabbing, sweeping and ploughing, sometimes feeding singly, communally or socially in loose or dense flocks (Battley et al., 2003). Prey items taken ranged from seeds of Widgeongrass Ruppia maritima to invertebrates (mainly polychaetes, molluscs and crabs) and fish, mainly juvenile Tilapia. The team also observed that during the day, main activities were feeding and roosting although a small fraction of the time (average of 10% for 25 species) was spent on comfort activities. After noticing that foraging behaviour and time were not species specific, they concluded that these behaviours vary depending on conditions of the feeding ground and indicate that water depth appears to be the key environmental factor controlling the availability of food for water birds in the Ghanaian lagoons. An earlier study by (Ntiamoa-Baidu, 1991b) on the seasonal changes in the importance of coastal wetlands in Ghana for wading birds revealed the peak months for waterbird (waders) abundance to be November and December. The study recorded 42 species of waders, comprising 29 Palearctic migrants, 8 residents, 2 migrants and 3 vagrants every month for 3 years in coastal Ghana. According to the study, most waders left the Ghana coast in January, leaving only a small proportion which remained until final departure in April. The study also reported that the proportion of migrant wader populations summering on the Ghana coast varied with species, and from year to year.

Social foraging in waterbirds in Ghanaian coastal lagoons was studied during October and

November 1994 by (Battley et al., 2003). The team identified two types of foraging were social: directionally synchronized flocks (often involving distinctive feeding methods used in unison) and dense pecking aggregations. They reported that social flocks were typically larger and denser than non-social flocks, and primarily involved piscivorous birds (fishing birds), especially the longer-legged shorebirds and egrets. According to them, it is probable that the flocks concentrate fish into temporarily high densities through herding or confusing escape

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reactions. They also go on to mention that there may be a true social element to either the initiation or persistence of waterbird social foraging flocks in coastal Ghana.

Ahulu et al. (2006) studied the food preference of the Common tern (Sterna hirundo) at the

Densu floodplains. They found prey materials such as exoskeleton of crab zoea larvae, capitellid worms, fish otolith, pieces of fish bones and vertebrae, detrital materials and sand grains were found in the guts of the Common tern. Their captivity experiment did not yield much because the common terns captured did not feed well in captivity; only one individual,

S. hirundo, fed on 15 specimens of the Banded jewelfish (Hermichromis fasciatus).

2.6.3. Diet of Black-winged stilts

The diet of Black-winged stilts varies strongly with seasons (del Hayo et al., 1996) but generally includes adult and larval aquatic insects , molluscs, crustaceans, spiders, oligochaete and polychaete worms, tadpoles, small fish and fish eggs (del Hoyo et al. 1996). Breeding

Black-winged Stilts choose sites close to water to enable foraging close to their nests. Black- winged stilts are precocial, the chicks usually feed on macro invertebrates in the breeding site upon hatching (Cuervo, 2003).

Hamilton (1975) also observed that stilts feed on insects using snatching feeding techniques and Pierce (1985) mentions that stilts often foraged standing during mayfly emergence to feed on emerging subimagines. It is without saying that Black-winged Stilts are generalists and feed on a wide variety of items; probably an adaptation to weather conditions. Thus their diet changes depending on the available prey items in the environment or area they find themselves.

Ntiamoa-Baidu et al. (1998) reports the diet of Black-winged Stilt to be fish and invertebrates.

The only limitation to their diet appears to be the size of prey; as long as the prey is small enough to be eaten it will be eaten

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Goriup (1962) observes that “none of the stilts was ever seen drinking, nor was drinking”. He explains that “it seems likely that sufficient moisture is usually obtained during swallowing items taken from water” thus satisfying water requirement, hence direct drinking is not necessary.

2.6.4. Disturbance, aggression and territoriality

Goss-Custard et al. (2006) point out that birds of prey do not only eat wading birds but also disturb them on the frequent occasions when attacks fail. Wading birds have to deal with disturbance from both predators and humans. They mention that disturbance to foraging wading birds by raptors causes energy expenditure by way of flight and those that were previously feeding lose feeding time by moving to alternative feeding sites where competition and interference may occur.

According to Goriup (1982), “an animal can adopt one of three basic responses towards its neighbours: aggression, tolerance or escape.” Nol et al. (2014) observed that aggression occurred in less than 10% of species. Goriup, (1982), observes that “There appeared to be a number of discrete feeding territories, comprising some 20 to 200 m of shoreline, used by pairs or individuals and defended from intrusion by other stilts. The birds present in these territories, however, changed from time to time, or were absent altogether: there were more feeding sites than stilts, and they seemed to be utilized on a first-come, first-served basis”. He mentions that

Black-winged Stilts exhibit vigorous nesting territoriality. He also indicates that “there appeared to be a number of discrete feeding territories, comprising some 20 to 200 m of shoreline, used by pairs or individuals and defended from intrusion by other stilts”, and notes that the birds inhabiting these territories changed from time to time and that at some times, they

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were altogether absent. This he reports owes to the fact that there were more breeding areas than there were stilts.

2.6.5. Foraging location and time

Obviously one of the most important factors that determines where a bird forages is the presence or absence of food items. Various birds species have varying techniques for detecting the presence of prey especially in water. Terns have been observed to identify areas of fish concentration off shore and their presence or absence serve as an indicator for fishers. (Goss-

Custard et al., 2006) indicate that within each 24-hr period, each bird needs to consume enough food to meet its daily energy requirements that is dependent on factors such as ambient temperature and other weather conditions, and that an individual bird achieves this by feeding in locations and at times of the day and “stages of the tide cycle where its intake rate is currently the highest”. They also indicate that Oystercatchers (Haematopus sp.) which are disturbed spent time and energy relocating to an “undisturbed shellfish bed”. This shows that disturbance is a factor that determines where waders feed and as previously mentioned by (Goss-Custard et al., 2006) the susceptibility of the wader to disturbance (by how much the disturbance reduces the intake rate) plays a role in site selection.

Goriup (1982) reports that Black-winged Stilts feed in all habitats from dry land to belly deep water although they are mostly at the water margins. One factor that seems to affect the choice of foraging location for waterbirds in general is the presence of water probably because it offers a range of different prey items to choose from. Ntiamoa-Baidu and others investigated the influence of water depth on the foraging behavior of waterbird species in 1998 and found that it was a major determinant of foraging location (Ntiamoa-Baidu et al., 1998). They assigned waterbird species to guilds (see Ntiamoa-Baidu et al., 1998) based on morphological traits and

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feeding behavior and found that the size and body morphology of the waterbirds influence the foraging location all being linked to water depth.

Robert & Mcneil (1989) report Black-winged Stilts foraging both day and night. Their results show that Black-winged stilts foraging at night fed on prey items different from what they fed on during the day. They also noted that during daylight, Black‐winged Stilts were predominantly visual foragers (75% attempts were pecking) and during night‐time, they used both visual (pecking) and tactile (multiple scythelike sweeps) techniquess. Goriup (1982) however, mentions that stilts foraging at night use tactile rather than visual cues to detect prey.

2.6.6. Foraging success and age

Schnell et al. (1983) indicates that when birds such as Brown Pelicans (Pelecanus occidentalis) use relatively complex hunting techniques, and that a fine-tuning of abilities develops with age.

Experience through learning makes better foragers. Juvenile birds most likely lack experience in prey detection and identification of suitable foraging sites with abundant or quality prey.

Ashoori, (2011) mentions that Black-winged Stilt chicks, despite being precocial still need parental care until fledging because they might not have become effective forgers to be able to fend for themselves.

2.6.7. Feeding techniques

According to Pierce (1985), Stilts are opportunistic feeders which respond to changes in prey abundance by changing their feeding style or by moving to other habitats. The Black-winged

Stilt, according to the guild system by Ntiamoa-Baidu et al. (1998) is a visual pelagic forager.

Pierce, 1985 mentions 9 feeding techniques for stilts in general and 6 techniques employed by

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the Black-winged Stilt Himantopus himantopus. He also mentions that stilts are able to “switch between feeding methods according to changes in the behavior or availability of their prey”

(Pierce, 1985). Earlier studies in the Northern hemisphere indicate Black-winged stilts feeds mainly by pecking at aquatic invertebrates in a variety of shallow-water habitats (Hamilton,

1975; Pierce, 1985).

Pierce gives an account of the feeding techniques he observed employed by stilts – techniques used by the black-winged stilts are as follows: (a) Pecking is usually employed by stilts feeding on nektonic prey. The technique involves the sudden thrust of the head forward “towards the prey which is snatched in the slightly opened bill”; (b) lateral probing, raking, filtering.

Swallowing (for all feeding methods) is assisted by a slower backward thrust of the head that also returns the head to its original search position.

Pierce (1985) reports that foraging stilts alter the position of their heads according to the abundance of their prey. When prey is scarce but conspicuous, the head is held high giving the bird a wide field of view. When prey is abundant the head is held close to the surface of the water. Pierce also notes that Stilts walked during all feeding methods, and further mentions that only during mayfly emergence in rivers did he find birds standing at one spot, waiting for emerging subimagines of Deleatidium to drift downstream into easy pecking range. Pierce also mentions snatching as a technique used by all stilt taxa.

Goriup (1986) mentions that the feeding techniques he observed of Black-winged Stilts are similar to those previously described by Hamilton (1975) for Black-necked Stilts: pecking, plunging and snatching. He also observed two new methods adopted by the Portuguese stilts as well as bill-pursuit which had previously been recorded only for Avocets.

Pecking according to (Goriup, 1982) was the commonest feeding technique used by stilts. He observes that

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“They walked or waded with a declined body, and a slight bobbing action caused by flexing the legs, while short jabs were made with the bill (fig. 3a). The items taken by males were visible more often than those taken by females, and particularly large, grub- like prey were dunked and washed before being swallowed. At nightfall, and by moonlight, the pecking-gait altered completely, becoming remarkably plover-like: the stance became quite erect, with the head held well above the shoulders. Locomotion was now a series of short runs followed by pecks, rather than an endless walk. The intervals were spent relatively motionless, with the head cocked to and fro, and it seemed that prey-detection had switched from visual to audial.” According to Pierce (1985), “Stilts feeding on nektonic prey feed mainly by pecking. During pecking the head is thrust suddenly towards the prey which is snatched in the slightly opened bill. Swallowing (for all feeding methods) is assisted by a slower backward thrust of the head that also returns the head to its original search position”.

Pierce (1985) explains that when pied stilts forage by pecking, the inter-individual distance is inversely proportional to prey density. He mentions that “distances of up to 15 bird lengths (c.

5 m) are defended at low prey densities”, and postulates that the observed behavior was likely for the purpose of minimizing disturbance from other birds, in the form of causing ripples of the water surface which may disrupt visibility. This feeding adaptation may also likely be a defense against disturbance of the water column that may cause prey to move away thus increasing search time.

Plunging is a feeding technique that involves the full submersion of the head into the water

(Hamilton, 1975). Goriup (1982) notes that plunging “appeared to be largely opportunistic, taking advantage of especially clear water or locally abundant submerged prey”. He observes that “a male once used this method for over 20 minutes, wading energetically in complicated figures and gyrations, kicking water up all around him, before plunging his head and neck into the water and propelling his bill in all directions, then emerging to swallow an item. The travel of head and neck was often so vigorous that a shower of droplets and a sizeable 'bow-wave' was produced”.

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According to Pierce (1985) plunging is “an underwater pecking and/or probing motion. In deep water the bill and head are totally immersed. Underwater pecking is used extensively by New

Zealand stilts, particularly in rivers and weedless lagoons and estuaries, where most prey live on or near the bottom”.

Hamilton (1975) did not observe bill pursuit for stilts but for avocets, he describes the technique; “rapidly opens and closes its bill (to a maximum extent of about one centimeter), while simultaneously moving it erratically along the water's surface. It appears that the bill is being used to pluck from the water some rapidly moving aquatic organism; however, I never observed an object large enough to be seen captured by this method.”

Goriup (1982) reports that “nearer the surface, bill-pursuit was used: the bill was half- immersed, and rapidly dabbled while chasing prey” and Pierce (1985) notes that it had only been recorded rarely in several stilt taxa.

Goriup (1982) reports his observation of the probing technique, and the semi-scythe; they

“were performed by a male in addition to the usual pecking method, during an evening feed.

When probing, he moved forward step by step along the shoreline, delving his bill vertically down in a series of short jabs, rocking his body to help provide the necessary thrust. When prey was caught, it was brought to the surface for swallowing. The bill could be sunk up to the hilt, with the head becoming partly submerged in surface water. The stilt would sometimes twist around to one side and behind in order to probe at an angle”. Pierce (1985) indicates in this non-visual method, the bill is inserted semi-vertically into a soft substrate to varying depths.

This method is used frequently by New Zealand stilts, but there are few records for overseas stilts. Some feeding actions appear to be intermediate between peck and probe, and may be a rapid probe or jab at a visually located site”. Hamilton (1975) described several scything

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behaviors for the avocet including the single scythe technique, where a partly-open bill is swept horizontally in a wide arc from one side of the body to the other, collecting prey on the way.

Goriup (1982) describes the semi-scythe for the Black-winged Stilt; “swept its bill through silt only from directly in front to a little on one side of the body before swallowing: I could not see if the bill was held partly agape, or if it was dabbled in a sifting action. In order to get the bill more or less horizontal, two postures were adopted, which 1 termed the 'Avocet' and the

'Flamingo'. In the former, the body was declined, with the legs deeply flexed. The 'Flamingo' involved the Black-winged Stilts keeping the legs nearly straight, with the head and neck curved under the body, and, when the sideways sweep was made, the silt just in front of the toes was sampled”.

Hamilton (1975) reports that filtering was not used by stilts however Pierce (1985) records this feeding technique for stilts; “in this non-visual method, the bill is rapidly dabbled and swept from side to side through mud or through surface algae or fine weed. I have seen it used frequently by pied and black stilts and once”. reports that snatching is a type of pecking where the stilt aims at a flying insect. “This opportunistic method is used by all stilt taxa examined, but never to the exclusion of other feeding styles” (Hamilton, 1975).

Ntiamoa-Baidu et al. (1998) report that the Black-winged Stilt used a wide range of feeding techniques and mention four they observed during their study at Keta and Songor Ramsar wetlands; probing, ploughing, sweeping and pecking. They mention that Black-winged Stilts foraged at water depths between 0-14cm, indicating that their diet consist of fish and invertebrates. The team observed that Black-winged Stilts fed throughout the day showing a

24hour feeding behavior and sometimes displaying social foraging behavior.

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Cavitt (2006) recorded five feeding techniques and added some specifications to the techniques earlier mentioned by David and Smith (2001) for easy detection. Some techniques can be similar to others depending on the posture of the bird and the depth of water it is feeding in.

They define pecking to involve <1/4 of the bill length penetrating the water, probing to be when

>1/4 bill lengths penetrated the water, plunging as the full submersion of the head below the water surface, scything to involve movement of the slightly open bill from side to side and filtering to involve the rapid opening and closing of the bill while moving over mud (Cavitt,

2006).

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CHAPTER THREE

3.0. Materials and methods

3.1 Study area

3.1.1 Location and size

The study was conducted in the Densu Delta Ramsar Site (DDRS) (Figure 3.1) which is the third largest coastal Ramsar site in Ghana with an original gazetted size of 58.9 km2 (Ramsar

Information Sheet, 2015). It is located on the outskirts of the city of Accra in the Greater

Accra Region and lies “in the valley formed by the Aplaku-Takuse and Weija McCarthy

Hills” 11km from Accra at (5°31’N 0°20’W) (Ntiamoa-Baidu & Gordon, 1991). The Densu

Delta wetland is also an Important Bird Area (RIS, 2015). The wetland basically consists of

“sand dunes, open lagoon, salt pans, marsh and scrub, which provide extensive suitable feeding, roosting, and nesting grounds for seashore birds” (Ntiamoa-Baidu & Gordon, 1991).

Figure 3.1: Densu Delta Ramsar Site

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3.1.2. Population and livelihoods

According to the Ghana Statistical Service Population and Housing Census (PHC) in 2010, the Ga South Municipality within which the DDRS is found has a population of 485,643

(about a tenth of the total population of the Greater Accra Region) of which 128, 727 are males and 134,015 females. The population of the Municipality is youthful (36.1%) with a small number of elderly persons (6.5%) (Ghana Statistical Service, 2012).

Densu delta provides a source of livelihood for many of the surrounding communities who exploit fish, crabs and other resources from the wetland. However, access to the portion of the area which is developed into salt pans for any activity other than salt mining is strictly prohibited. The salt mining industry (Figure 3.3) provides employment for hundreds of community members around the wetland. There were 485,700 people living and working in the area in 2015 (RIS, 2015).

Aside salt mining, the other main economic activity is fishing. It is undertaken mainly by the people from the fishing villages located on the sand dunes such as Tsokomey and Faanaa, however, fishermen come from other areas in Accra to fish in the lagoon. Fish catch is seasonal and dependent on the water level; highest when water level is moderate, low when the lagoon dries up and none during floods as fishing is impossible during periods of flood. Acadja/ acaday fishing where branches of mangroves are placed in the water to trap fishes had been introduced in the past (Ntiamoa-Baidu & Gordon, 1991; Oteng-Yeboah, 1999). Generally, fish catch has been declining and the fishermen attribute this to the increase in numbers of fishermen and seasonal flooding (Kondra, 2016).

Other activities in the wetland include harvesting of Blue-legged swimming crabs using traps, mangrove cutting for firewood, collection of sedges and reeds (mainly Imperata, Cyperus and

Typha) for thatch and mats, cattle grazing and hunting of Heron and Tern species (Ntiamoa-

Baidu & Gordon, 1991).

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3.1.3. Land use and ownership

The DDRS, as an internationally important wetland under the Ramsar Convention is managed by the Wildlife Division of Ghana (Gbogbo, 2007b) and the Panbros Salt Industry (a private investor). However, a greater portion of the site is managed by the Panbros Salt Industry. The land, however, “is held in Trust by the Ghana government for the people of James Town”,

Panbros procured a concession of 11.3 km2 (Ntiamoa-Baidu & Gordon 1991). Despite the protection efforts and management approaches, recent records indicate that the wetland has suffered a 22% reduction in land size between 1992 and 2007 (Gbogbo 2007; Kondra 2016) and it is likely that further reduction has occurred since 2007 till date. A significant portion of the area (18km2) has been developed into salt pans for commercial salt production (Gbogbo,

2007a). The eastern end of the area is bounded by human settlements which continue to encroach heavily on the wetland (Figure 3.2). Surrounding communities include Aplaku,

Tetegbu, Bortianor, Panbros and Weija; Gas are the major ethnic group in the area but there are some Ewes along the shoreline (Kondra, 2016).

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Figure 3.2: Map of Densu Delta Ramsar site showing settlements around and within the wetland

Figure 3.3: Commercial salt mining (Image source: Daniel Domashie)

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3.1.4. Climate

The DDRS lies within the Densu floodplains. The Municipality lies in the dry equatorial climatic zone with two rainfall seasons. The mean annual rainfall varies between 790mm along the coast to about 1270mm in the extreme north. The annual average temperatures range between 25.1ºC in August to 28.4ºC in February and March, which are the hottest months. The relative humidity is about 75% in February and March (Ghana Statistical

Service, 2014).

The area experiences periodic flooding especially between May and June when the Weija dam located upstream is opened to discharge excess water from the dam (Kondra, 2016). This seasonal event results in an increase in water level that halts all commercial activities.

3.1.5. Vegetation

The DDRS constitutes the lower reaches of Densu River’s water course where it joins the

Gulf of Guinea (Gbogbo & Attuquayefio, 2010). It lies in the Savannah agro-ecological zone

(GSS, 2014). Ntiamoa-Baidu & Gordon (1991) describe five main habitat types in the wetland namely sand dunes, salt pans, brackish lagoon, freshwater marsh, coastal savannah and thickets, which still occur in the site. As they indicated earlier, there is very little vegetation on the sand dunes and in the salt pans. Coconut trees Cocos nucifera line the dunes, and Sesuvium portulacastrum is found on the fringes of some salt pans and on the dykes in the pans. A few scattered mangrove stands can be found in some parts of the lagoon and these are heavily exploited. In the less saline areas, approaching the entrance of Panbros the vegetation is mainly Imperata cylindrica, Typha sp, Cyperus articulates, Avicennia africana and Sporobolus virginicus stands. A few trees can be found scattered throughout the site which serve as perches for terrestrial birds such as Pied Crows (Corvus albus).

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3.1.5. Faunal composition

The DDRS provides sanctuary for resident and migratory waterbirds, with a record of 57 species and a total waterbird population of 35,000 at the time of designation in 1992 (RIS,

2015). Common species found at the site include the Spotted Redshank Tringa erythropus,

Curlew Sandpiper Calidris ferruginea, Little Stint Calidris minuta, and Black-Winged Stilt

Himantopus himantopus (Ntiamoa-Baidu & Gordon 1991; Grimble et al., 1998; RIS, 2015).

Ntiamoa-Baidu & Gordon (1991) report 70 species of land birds and indicated that this was not the complete list. A comprehensive list of land birds at the site has not been compiled.

The Laughing Dove (Stigmatopelia senegalensis), Yellow-throated Longclaw (Macronyx croceus), Senegal Coucal (Centropus senegalensis) and Vinaceous Dove (Streptopelia vinacea) were observed in the wetland during the study period. Fifteen species of fish have been recorded, with Tilapia zillii and Sarotherodon melanotheron being the dominant species. The beaches are also known to be breeding sites for marine turtles, notably the Green turtle Chelonia mydas, Olive ridley turtle Lepidochelys olivacea and the Leatherback turtle

Dermochelys coriacea (RIS, 2015). The vegetation that lines the roads and footpaths serve as habitat for rodents; they can be seen moving between vegetation patches.

3.1.6. Geology and Soil

The land area is underlain by shallow rocky soils and basic gneiss inselbergs. The main type of soil in this area is the Coastal Savannah Ochrosols. The coastal sands are pale yellow in colour and without humus or organic matter. These soils are rich in sandstone and limestone that are good source of material for the construction industry (Ghana Statistical Service,

2014). The soil within the wetland is soft and muddy and smells like Sulphur.

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3.1.7. Relief and drainage

The land area of the Ga South municipality consists of gentle slopes interspersed with plains in most parts and generally undulating at less than 76 metres above sea level. The hills surrounding the wetland send runoff during rains to be drained and cleaned in the wetland before entering the sea. There are two main rivers namely, the Densu and Ponpon River, which drain the Municipality. Densu is one of the main sources of water supply to more than half of the population of the Accra Metropolis (Ghana Statistical Service, 2014).

3.1.8. Hydrology

The Densu Delta Ramsar wetland is fed by the Densu River which is dammed 11km upstream by the Weija dam, one of two dams that supply water to Accra (Ntiamoa-Baidu &

Gordon, 1991). The Weija water works management controls the inflow of freshwater into the wetland. However, the discharge only occurs from July to November and the maximum discharge permissible is 200m3 per sec. This limit, according to Ntiamoa-Baidu & Gordon

(1991) is imposed to protect the bridge over the Densu River along the Accra-Winneba road.

The water level in the wetland is generally low in most parts of the wetland. In the river and during flooding, the level of water can reach up to 2m. The water temperature ranges 25℃-

30℃ (RIS, 2015).

3.1.9. Threats

The main threats facing the wetland include encroachment by settlements and buildings on designated lands. The Panbros management has done its best to control the takeover of the wetland by settlers. However, its efforts seem to have only minimized the rate of encroachment as new buildings keep sprouting up and further developments are taking place.

Kondra (2016) report the level of buildup in the wetland including completed and uninhabited houses, and disposal of waste into the lagoon, due to lack of waste disposal

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systems. Oteng-Yeboah (1999) earlier observed that “many new houses are built directly in the wetland, and some are adjoined to the saltpans. Large-scale estate and property developers such as Vanderpuye-Orgle Estates Ltd. own large parts of the land in and around the wetlands”. (Boafo et al., 2014) also note that many of these settlements have no proper planned sewage disposal strategy, thus waste is dumped directly into the wetlands or the sea.

Open defecation is common in the wetland and along the beach (Kondra, 2016).

During the rainy season, the wetland gets flooded and the flood water is discharged into the sea. These seasonal flooding events bring detritus, nutrients and pollutants into the wetland

(Osei et al., 2010) from neighboring upland areas such as settlements in Weija, McCarthy

Hills, Gbawe and Mallam. The presence of the dam is a threat to the water regime in the wetland; sediment build up behind the dam blocks outlets and lowers the volume of water discharged into the wetland (Addo et al., 2018). Oteng-Yeboah (1999) projected that the trapped sediment in the dam lowers the sediment load in the wetland and may cause erosion of the shoreline. This might probably be a contributing factor to the current problem of erosion faced in the area.

3.2. Methods

3.2.1. Study site selection

3.2.2. Breeding ecology

Breeding sites were selected by observing breeding pairs. Many sites were used by the Black- winged stilts for breeding but three were important for the study. Other places did not have more than a nest or two. During the preliminary study, only sites with five or more nests were selected for the study. The three selected sites experienced different levels of disturbance;

Site 1 was relatively undisturbed (RELU), Site 2 was relatively most disturbed (REMD), and

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Site 3 was relatively most undisturbed (REMU) (Figure 3.4). The intensity of disturbance was however not measured or quantified because it is beyond the scope of this study

Site 1 (RELU)

This site (5°32'7.16"N, 0°16'54.42"W) was an old salt pan that was no longer operated and is relatively undisturbed, with disturbance coming from occasional passing vehicles and fishermen moving to and from surrounding towns on foot. The pans at this site contained water throughout the study period. Nests were constructed on levees in the pans, on the side of the levees in the pans and inside the pans on heaps of mud and pebbles.

Site 2 (REMD)

Site 2 (5°31'53.10"N, 0°17'13.74"W) was adjacent to Site A but separated by a distance of about 300 meters. Site 2 was also an old salt pan that was no longer in use. Site 2 was the most disturbed relatively, of the three sites; it was close to a fishing hub where both fishermen and market women came to sell and buy fish. Traders from the neighboring settlements also came there to sell food to the fishermen and market women. Some fishermen as well as crab collectors came to the area with their dogs which posed a threat to the Black- winged Stilt nests and eggs. The site was also close to a busy road with a lot of vehicular traffic. This site experienced periods of dryness during the dry season and became inundated after the rains.

Site 3 (REMU)

Site 3 (5°31'12.80"N, 0°17'53.15"W) was a flat land adjacent to a river and mudflat. It was about 900m away from the estuary and most parts of it were covered by Sessuvium portulacastrum which served as nest material for Black-winged Stilt nests. Site 3 was the most undisturbed relatively, of the three sites with very little disturbance coming from the

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occasional fishermen moving to and from the estuary in boats but not close to the nesting area. This site was wet throughout the year but not inundated.

Figure 3.4: Sites at the Densu Delta Ramsar site used for Black-winged Stilt breeding studies

3.2.3. Foraging ecology

The various sites for the study were selected after a reconnaissance visit to the wetland. At the beginning of the study most places were dry due to the dry season, and only a few places such as the salt pans and ponds that supply water or channel water to the pans were filled with sea water pumped from the sea. These places however were largely not used by the

Black-winged stilts and for that matter other waterbirds due to the salt mining activity that constituted human disturbance. Time budget, activity rhythm and foraging behavior observations were carried out close to the estuary because other places were dry at the beginning of the study. Three months after the start of the study, the birds shifted to other places to forage and roost. Observations continued at these new places, so the feeding

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behavior data were collected at three main sites: (i) Estuary (ESTF), (ii) Foraging site 1

(FORS1) and (iii) Foraging site 2 (FORS2) (Figure 3.5). These three sites are described below. There was a fourth site close by that was used as a roost site when the tide was high and foraging was impossible or when the temperature was high and the birds had to rest.

Measurement of the sites was done using remote sensing tools in Google Earth®.

Foraging Site 1 (FORS1)

This site with 108,752 m2 (0.108km2) of open water was a fresh water marsh used by some local people for fishing. The most abundant fish caught was the Black-chinned Tilapia

Sarotherondon melanotheron. The site served as feeding site for Terns, Heron/Egrets, ducks and other long-legged waders. There was temporal flooding of this site at certain times of the day corresponding to the tide. The northern side was lined with shrub vegetation and some mangroves which were harvested for ‘acadjay’ fishing and as fuel.

Foraging Site 2 (FORS2)

Foraging Site 2 was adjacent to Foraging Site 1 and had an area of 13,671m2. A small channel separated the two sites. This site was also marshy with shrub vegetation and mangrove stands surrounding it. Some local people used canned food tin traps to catch crabs at this site. Apart from the Black-winged Stilt, Common Moorhens (Gallinula chloropus) were observed foraging under the mangroves and the emergent vegetation (stumps) and acadjay systems were used by Long-tailed Cormorants (Microcarbo africanus) as roosting perches.

Estuary Foraging Site (ESTF)

This site (5°30'52.67"N, 0°17'55.31"W) had an area of about 101,347m2 (0.101 km2) and was at the estuary where the river empties into the sea. The area was very dynamic with

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fluctuating water depths corresponding to the rise and fall of the tide. The substrate was muddy and at certain times of the day, small silt islands emerged. The surrounding land was covered with Sessuvium portulacastrum. There were lots of crabs in the area and Whimbrels

(Numenius phaeopus) were observed feeding on them.

Figure 3.5: Sites used by Black-winged Stilts for foraging and roosting.

3.2.4. Time activity budget

Black-winged stilt flocks were monitored during 12-hour periods (6:00am to 5:00pm) for 10 minutes at each site using a pair of binoculars (Vortex® Diamond-Back 8x40). The flocks were observed hourly for a minimum of 10 minutes and individual activities as well as the number of individuals doing the activities were recorded for each time period. For individuals that engaged in more than one activity during the hourly scan, a particular activity is recorded when after one minute of observation that activity was engaged in 50% or more of the time.

The activities recorded were foraging; bathing, stretching and preening (collectively treated

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as comfort activities); flying; standing; resting; walking; running; and courtship behavior, nesting (nest construction), and brooding during the breeding season.

The Black-winged Stilts flocks moved at certain times of the day from one site to another.

Observations were paused and continued when the flock retuned. However, if the flock settled close by the researcher, the flock was followed and observations continued.

3.2.5. Breeding ecology

The breeding ecology data were collected from March –July 2016 during preliminary study and April to July 2017, the period when Black-winged stilts are known to breed in Ghana. The breeding sites were visited three days a week from April to May when egg laying occurred, followed by daily visits in June and July when hatching was expected. During these periods, activities of the Black-winged stilts were observed and recorded using a pair of binoculars

(Vortex® Diamond Back, 8*40).

3.5.6. Nest monitoring

Each nest encountered was monitored regularly from the day it was first encountered till the eggs hatched or got missing. Nests were usually constructed on the ground making it difficult to see if it contains no eggs, hence courtship behaviour amongst breeding pairs was used as a cue to locate active nests and then follow up visits were made. Brooding activity was also used to locate some nests. In some cases, breeding pairs attempted to lead the researcher away from the nest by pretending to have a broken wing or by false brooding at a different spot.

The position of each nest was marked using wooden pegs at a distance of 30cm for identification during subsequent visits. The location of the nest was also recorded using a handheld GPS device (Garmin etrex 10x). During the monitoring, some nests showed proof depredation or displacement of eggs by flooding; for others it was unclear the cause of the disappearance of the eggs. Ecological associations such as interspecific competition and

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interferences were observed and documented as measures of disturbance. The eggs of the

Black-winged stilt are camouflaged when laid on the bare ground, thus, care was taken to avoid trampling on eggs during the monitoring. During the hatching period care was also taken to avoid stepping on hatched chicks. Also, time spent at each nest was limited to between 5-10 minutes to reduce the likelihood of leaving behind olfactory cues that lead predators to the nest.

This was also done to reduce the time the nest is not attended as prolonged periods of nonattendance could lead to nest failure. Prolonged presence of researchers at the nest may also cause the nest to be abandoned (Hansen et al., 2011).

3.2.7. Nest success

A nest was successful when at least one egg out of the clutch hatched. This was indicated by the presence of a chick in the nest during monitoring, shell fragments or a chick nearby when the date of monitoring coincides with expected hatching date or a chick is observed with an adult within the vicinity. Nests that did not meet these criteria are considered failed nests; in addition to visible signs of depredation; spilled egg content; or evidence of flooding when there was a downpour prior to field visit. In the case of a likely nest failure, when these conditions are not met, the immediate area of the nest is scanned for prints to determine the cause of the missing egg(s). The number of eggs that hatched in a nest was expressed as a fraction of the total number of eggs. For each site, the total number of nests, total number of eggs, number of successful nests and number of eggs that hatched were computed. Factors that were responsible for nest failure such as predation by small mammals, reptiles, birds of prey and domestic animals such as dogs; and flooding were noted.

3.2.8 Incubation period

During the breeding period, the total number of nests encountered was recorded and days for first egg laid noted and monitored until the last egg is laid. The incubation period was then

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estimated for successful nests that were monitored from egg laying till egg hatching as the number of days from brooding till hacthing. The times of the day during which the breeding pair brooded the nest were recorded in relation to other activities done in a day.

3.2.9. Parental care

The behaviors of breeding pairs before and after hatching of the eggs were investigated. The relationships between the breeding pairs and hatchlings also were documented. Black-winged stilts are precocial and hatchlings were observed leaving the nest as early as within an hour of hatching if there was an imminent threat. Parents are also known to be very aggressive after hatching. Aggressive behaviors and deterrent methods were documented for the Black-winged stilt breeding pairs.

3.2.10. Measurement of Egg Length, width and weight

The length of each egg was measured using a veneer caliper around the fullest vertical cross- section of the egg while the width of each egg was measured using a veneer caliper around the fullest horizontal cross-section of the egg.

The weight was measured using a spring balance in situ. The egg was placed in a pouch attached to the spring balance for measurement. The site was windy most of the time so care was taken to shield the pouch and balance from the wind to avoid interference with the measurement.

Other measurements taken

The distance of the nest from the road was taken as a measure of disturbance from human pedestrians. This was done using a range finder. For nests that were in the water, the ruler function in Google Erath ® was used to estimate the distance of the nest to the road using the coordinates of the nest taken. The distance of a nest to the nearest nest was also measured

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using the ruler function in the Google Earth software. The measurement was made from the relative positions of each nest as obtained from the GPS coordinates recorded by overlaying the coordinates on a physical map.

For each nest, the presence or absence of vegetation and water around the nest was documented. The water could either be in the pan next to the nest or surrounding the nest for nests constructed on mounds in the pans.

3.2.11 Foraging ecology

Data were collected from September 2017 to April 2018. A reconnaissance scan of the study site was conducted to identify potential foraging sites of Black winged stilts. Black-winged

Stilts foraged at different sites and moved between sites. The one factor that appeared to influence choice of foraging site was the presence of water. Black winged stilts were not seen foraging on dry patches of land within the study site and when a patch used for foraging dried up, the flock moved to another patch with water.

3.2.12. Macroinvertebrate sampling

Benthos samples were taken at two sites at the Densu Delta wetland with a handheld corer

(9.6cm) where Black-winged Stilts had been observed to forage. One site was an area of open water that was shallow at the edges; there was water here all year. This site (5°31'22.14"N,

0°17'13.53"W) was bordered on the southern side by dense unplanned settlements. The second site was at the estuary (5°30'55.41"N, 0°17'52.69"W) (check site description for estuary under foraging sites). Due to the depth of water at the estuary as reported by the local fishermen, it wasn’t possible to sample during the high tide so samples were taken only at low tide when the substrate was exposed for foraging birds, however, some places still had some water (about 0.5m high). Sampling stations were about 150m apart at the wetland site and a minimum of 100 meters at the estuary. Sampling stations at the estuary were placed in

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order to capture the different microhabitats; open water areas, near grass (Sessuvium portulacastrum), near mangroves and close to the shoreline. GPS coordinates were taken at each sample location. Seven stations were sampled at the open area and 4 at the estuary.

Core samples were taken to a depth of 15cm and washed in situ with a 1mm nylon sieve. The top 5cm was washed separately from the bottom 10cm to investigate the portion of macroinvertebrate community easily available to the Black-winged Stilt. Three replicates were taken at each station. Organisms found were fixed in 70% formalin and transported to the laboratory for storage and identification. During the low tide periods at the estuary, the water level was too low to wash the sediment so core samples were bagged and transported to the lab, washed immediately and fixed in formalin for later identification. Rose Bengal was added to the formalin to dye the soft bodied organisms to facilitate identification as the formalin would cause discoloration. Hand gloves were worn at all time when dealing with formalin during fixing and transportation of fixed samples to storage locations.

Macroinvertebrate densities were calculated for each sample take and expressed per m2.

() =

= 4

Where, d=diameter of corer

3.2.13. Foraging behavior

The behavior and style of feeding for Black-winged stilts at the Densu Delta Ramsar wetland was documented using direct field observations and video recordings. The observations recorded included, feeding behavior and intake rates; the water depth and nearest neighbor distances were also recorded. A particular individual was videoed after it had been observed

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to be foraging by using one of the foraging styles described below. This was to ensure only active foragers were used for the analysis. Videos usually lasted between 3 and 5 minutes or until the bird flew away or the observer lost track of the individual. Video recordings that lasted shorter than a minute were not added to the analysis. The videos were transcribed using the Solomon Coder software. Intake rates, style of feeding, and general behavior of foraging individuals were extracted from the videos taken. Feeding styles followed descriptions adapted from Goriup (1982), Ntiamoa-Baidu et al., (1998) and Davies & Smith (2001) are as follows:

Pecking : <1/4 of bill length penetrates the water substrate and involves short rapid jabs at the surface (water surface or soil/silt). This feeding style is usually accompanied by an endless walk by the Black-winged stilt. Occasionally, there is a short pause to swallow.

Probing: >1/4 of bill length penetrates the water surface and involves delving the bill vertically down in a series of short jabs, rocking the body to help provide the necessary thrust. When prey was caught, it was brought to the surface for swallowing. The bill could be sunk up to the hilt, with the head becoming partly submerged in surface water.

Plunging: This method is used opportunistically, taking advantage of especially clear water or locally abundant submerged prey. Plunging involves the submersion of the entire head into the water to take prey items. The head emerges from the water after a prey item is caught to swallow.

Scything: For this method, the bill is opened and rapidly moved from side to side in a horizontal fashion. Prey items are picked up as the bill moves and then swallowed.

Filtering: This method involves rapidly opening and closing the bill while moving over mud or the water surface. Prey items are opportunistically caught by the bill and swallowed.

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The number of prey items taken per unit time was computed as intake. A feeding attempt was successful and deemed an intake if the individual under observation was observed to hold a prey item in its bill prior to swallowing or it showed swallowing movement after showing foraging behavior. Intake rate was defined as the number of successful attempts divided by

the number of attempts. () =

Intake percentage was computed as the intake rate expressed as a percentage.

(%) = ∗ 100

3.2.14. Water depth measurement

The depth of water was estimated using the relative proportion of the leg that was exposed above the water surface. The exposed vertical length was assigned a value on a scale of 0.1 –

1.0 at 0.1 intervals following Ntiamoa-Baidu et al., (1998). Thus 0.1 when the water was very shallow or on dry land and 1.0 when the bird was standing in belly deep water. These scale values were converted to actual lengths.

The distance to the nearest neighbor was estimated for both conspecifics and heterospecifics using a range finder- for neighbors closer than 2 meters, estimation was done during video playback. A maximum value of 100m was assigned when an individual was observed to be foraging in a particular location alone.

3.2.15. Data Analysis

The time-activity-budget of the Black-winged stilt was computed as the proportion of time spent on each activity per time period. This was expressed as a fraction of the total observation time and presented graphically using the Microsoft Excel ® package.

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Nesting data were entered into Microsoft Excel spreadsheets. The number of nests and the eggs encountered in them as well as the total hatches were documented. The R software was used to analyze and graphically present the data. The variables were tested for normality and appropriate parametric or non-parametric tests were applied. The proportions of eggs laid during each breeding season and at each breeding site were calculated. The proportions of successful and unsuccessful nests were also computed for both years and at each breeding site, and for nesting location.

Kruskal-Wallis tests were performed to investigate the relationships between the various breeding sites in terms of environmental parameters, egg morphometrics and response of breeding birds to predators or intruders. Bonferroni post hoc tests were performed to further determine the source of difference if the Kruskal-Wallis tests show significant differences between the breeding sites. The same variables were tested for relationship between the two study years using Wilcoxon signed-ranked test.

Binomial logistic regression models were fitted to explore the relationship between nest success as response variable and nesting properties as explanatory variables; distance to road, distance to closest nest, minimum permissible distance, egg length, egg width and egg weight.

For variables with missing data, the mean of available observations was supplanted to fill the gaps. Nest success is a categorical variable with two levels; thus, ranks were assigned for the model to be computed; 1= unsuccessful and 0= successful.

Generalized linear regression models were fitted to explore the factors that influence the degree of egg hatchability. The number of eggs that hatched per nest was used as the dependent variable with environmental parameters, nesting properties and egg measurements as the independent variables. The response variable was numeric and from 0-4; 0 for failed nests and

4 the highest number of eggs hatched.

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Model selection was done using the Akaike’s Information Criteria (AIC) doing a stepwise forward model selection procedure. The model with the least number of predictors and the lowest AIC value was selected as the parsimonious model and thus the best fit model. Models with AIC values differing by less than 2 were considered to be equivalent.

The frequency and duration of each feeding style and activity were computed. The rate of each activity was defined as the time spent on the activity divided by the total observation time.

Kruskal-Wallis was used to test how the three foraging sites differed in terms of the number of foraging individuals and the method of foraging used by the Black-winged stilts. The R software was used to explore the association between environment factors and how they influence foraging flock number, feeding method and foraging rate. Linear regression models were computed and the best model selected using Akaike Information Criteria (AIC).

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CHAPTER FOUR

4.0 Results

4.1 Breeding ecology

4.1.1 Nest construction

Black-winged stilt’s nest construction started late March in 2017, however in March 2016 when the preliminary studies were done, some eggs had been laid already. Initially, only a few individuals were observed at the breeding sites. Nesting individuals were temporarily displaced from their nest when disturbed by humans to seek refuge on foraging grounds. Initial signs of nest creations included observation of scratches or depressions on grounds where nests were to be constructed. These scratches appeared to have been made during the early hours of the morning when the substrate was soft due to morning dew. Later in the day when the sun began to shine, the substrate hardened and became compact, and the birds were observed to halt nest construction, with the exception of a few pairs who were constructing their nests in the salt pans. Many of the nests were scratches on the ground with little or no material added. This nesting method offered more camouflage and made the already cryptic eggs more unnoticeable.

The identification and monitoring of nests had to be carried out with care to avoid trampling the nests and eggs, as in many areas it was difficult to spot nests and the eggs contained in them.

A pair of Black-winged Stilts was observed constructing their nest inside the salt pan with stones, mud chips and pieces of algal mats. They first selected the site for the nest, then started picking up nearby stones in the shallow water and piling them up at the selected nest location.

They would pick the stones and toss them close to the nest and then move closer to add these stones to the nest.

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Nesting material

While some Black-winged Stilt nests were simple depressions on the bare ground, other nests were constructed with a range of materials which could be grouped into four categories: (i) grass (fresh and/ or dried); (ii) dried mud chips; (iii) feathers; and (iv) pebbles (Plate 4.- Plate

4.). Figure 4. shows the frequency of use of different materials for nest construction by the

Black-winged Stilts.

4% 2%

10% Bare ground Pebbles 23% Mud chips 61% Grass

Feathers

Figure 4.1: Proportion of nests constructed with different materials.

Plate 4.1: Scratches on the ground to form slight depression for nesting on bare ground.

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Plate 4.2: Nest under construction with old feathers as nesting material

Plate 4.3: A nest constructed with a variety of materials (mud chips, twigs, feathers and other random materials).

Plate 1.4: Black-winged stilt nest with three eggs. (Eggs laid in depression in the ground and surrounded by twigs, pieces of crab exoskeleton, feathers and dried mud chips)

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4.1.2 Nest location

One hundred and fifty-four (154) nests were found on the dykes and 5 in the pans during the

2016 breeding season. For the 2017 breeding season, 51 nests were found inside the pan and

67 nests on the dykes. Of the nests recorded in 2016, 48 had vegetation around them while 111 nests had no vegetation around them. Eighteen of the nests located in 2017 had surrounding vegetation and 100 had no vegetation. With the exception of 8 nests in 2016 that did not have water around them, all other nests had water around.

A total of 277 nests were located and monitored during the study. One hundred and sixty-nine

(169) nests were depressions on bare ground while the remaining 108 nests were made of a range of nest materials.

4.1.3. Nest recycling

Nest recycling is when a nest previously used is reused either by the same breeding pair or another pair. Nest recycling was observed among Black-winged Stilts during both the 2016 and 2017 breeding periods. In the study area, flooding during heavy rains washed most of the nests away so only a few nests survived till the nest breeding season. Fresh eggs were sometimes encountered in nests that had previously been depredated or washed away. It is however unclear if the same breeding pair was reusing their old nest or a different pair as it is not possible to mark the birds. Other waterbird species eg, Collared Pratincoles and Little terns also were observed laying in old Black-winged stilt nests.

4.1.4. Nesting Area properties

The distance of nests to the road ranged from 5 m to 279 m with a median of 87 m. The highest range was recorded at the site RELU followed by site REMD with the site REMU having the lowest range (Figure 4.). Few nests were found at site REMU - one nest in particular was found about 200m from the road in a colony of Collared Pratincole nests. Kruskal-Wallis test showed

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that there were significant differences in the Nest distance to road among the sites (x2 = 50.501, df = 2, p-value = 1.081e-11). Bonferroni test showed that nest distance amongst all three sites differed significantly (p-value, RELU-REMD=5.44e-13, RELU-REMU=2.67e-9, REMD-

REMU=1.41e-5).

The shortest inter-nest distance was <1 m and the longest distance was 102 m with a median of 10 m. Kruskal-Wallis test showed no significant difference in inter-nest distance among the sites. Figure 4. shows the relationship between the median distances to closest nest among the three sites.

Figure 4.2: Boxplots of the distances of nests to road at the various Breeding Sites. Site RELU is relatively undisturbed, Site REMD is relatively most disturbed and Site REMU is most undisturbed.

Figure 4.3: Boxplots of the distances of nests to closest neighbor at various breeding sites. Site RELU is relatively undisturbed, Site REMD is relatively most disturbed and Site REMU is most undisturbed.

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4.2 Mating behavior

Despite several hours of observations, only a single observation of mating behavior was recorded. This happened with a female Black-winged stilt foraging among a loose flock of about 23 individuals. Suddenly a male flew in, moved close to the female and initiated a courtship ritual. The female appeared to be filtering and scything intermittently but never raised its head or lifted the bill out of the water. This appears to be the soliciting posture as this position was maintained throughout the process. The male drew closer to the female which started to turn away but still had her bill in the water. She did a 360° turn while the male followed at about 10cm. She stopped turning, still had her bill in the water displaying scything, filtering and pecking behavior; the male was now on her right side. He pecked at the water a few times, preened briefly for about 2 seconds and circled the female from behind to stand on her left side. He filtered and pecked at the water while moving.

At this point, the female’s bill was out of the water but was still in the soliciting pose with her tail raised up and head held downward. The male preened for a while on her left side, then moved to the right side going behind her, pecked briefly and preened. He repeated this cycle of the movements one more time. Finally standing on her right side, he inched closer while scything sharply and raising his head. This motion was repeated 13 times before he finally mounted her and raised his wings up perpendicular to his body. It took one second for them to balance, the female appeared to have knelt down briefly, coming up, their cloacae made contact and the male dismounted. He walked away preening, while the female stood in place also preening. The entire episode lasted 1 minute 11 seconds.

4.3 Nesting behavior

4.3.1 Brooding

After egg laying, the breeding pairs were observed to take turns to brood and repair the nest by continually adding pebbles and other material to the nest. They alternated brooding duty with

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foraging activity. One parent brood the nest or stays around to protect the nest as the other goes off to forage. They switched and continued like this all day, coming together to add materials to the nest occasionally before switching roles. Breeding pairs were not marked so it was not possible to measure the amount of time each individual spent at the nest. The nests were never left unattended to during the brooding period. Nests with neither of the breeding pair present signaled abandonment.

4.3.1 Nest protection

Nesting couples were very aggressive throughout the entire breeding period. Aggression however greatly increased during hatching of eggs. During nest construction, Black-winged

Stilts abandoned empty nests when disturbed. These nests were observed to remain empty for a while, but eventually eggs were laid in it. It is however not clear if the same parents that abandoned the nest previously returned to it or another opportunist pair had come to use it.

After egg laying, the breeding pairs exhibited very aggressive behavior, which mostly comprised of high-pitched vocalization while flying about. The aggressive birds would even swoop down close to the observer (researcher) in an attempt to drive the observer away from the site, and in most cases, they made contact with their wings. On several occasions, they left trickles of water on the observer’s neck after contact. Sometimes the observer had to leave the colony and wait till the birds were less agitated before continuing with the observations.

There were instances when Yellow-billed kites (Milvus migrans parasitus) flew close to the breeding site. They were met with very aggressive displays and mob action. Some members of the flock flew up and drove the kites away. In some cases, only one Black-winged stilt tackled the kite and drove it off. Pied crows Corvus albus also caused disturbance, they mimicked the

Yellow-billed kite and swooped down in an attempt to collect chicks or juveniles in the flock.

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None of the predatory attempts of the pied crows was successful during the study period because each attempt was met with aggression from the Black-winged Stilts.

Black-winged stilts did not even permit any other wader or shorebird species to cross their territory. In one case, a breeding pair intercepted a flock of little terns moving between roosting sites and knocked one individual into the pan. Prior to hatching, nesting Black-winged Stilts could accommodate and share resources, i.e. space with other species. However, as soon as the hatching period began, they became very aggressive, even attacking herons and egrets that came too close.

A range of behaviors were employed by the Black-winged stilts to deter intruders from their nests. The most notable was the very aggressive noise and close-range flight near the intruder.

Other forms of aggression included scary aerial displays or dropping faeces on intruders (Plate

4.2). The Black-winged stilts also did the “broken wing display” at a distance from the nest to lead the intruder in the wrong direction. This display is done to lure the intruder or predator away from the nest by offering easy and better prey, which is the bird posing as though it had a broken wing. A predator is likely to abandon the search for eggs and go for the wounded bird who would take to flight when the predator came close enough. Two things were achieved by this strategy: (i) the predator does not get the eggs or chicks and (ii) the predator is lured away from the nest. Black-winged stilts also pretended to be drowning sometimes to lure predators away from their nests.

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Plate 4.2: Black-winged stilt dropping on researcher

4.4. Minimum permissible distance

The minimum permissible distance (i.e. the minimum distance nesting birds at the various sites allowed before initiating deterrent or aggressive behavior) ranged from 4m to 41 m with a median of 15.79. Figure 4. shows the distribution of the minimum permissible distance recorded at the different sites. Kruskal-Wallis test showed significant difference (x2 = 16.656, df = 2, p-value = 0.00024) among the sites. Bonferroni’s test revealed that the difference was between sites RELU and REMD (p-value=0.04) and between RELU and REMU (p-value =

0.05). The difference between sites REMD and REMU was not significant (p-value = 0.5).

The distance breeding pairs allowed before initiating deterrent or aggressive behavior seemed to be closely related to the stage of the nesting season. At the onset of brooding, the minimum permissible distance was low, with birds allowing close approach before initiating aggressive behavior. However, during hatching period, the minimum permissible distance increased significantly with aggressive behavior, being initiated at about 30 meters to the breeding site.

There was no significant association between minimum permissible distance and clutch size

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(Figure 4.5) suggesting that the number of eggs in a nest did not determine the minimal distance allowed before deterrent behavior or aggression is exhibited.

Figure 4.4: Minimum permissible distance by Nest site. (Site RELU is relatively undisturbed, Site REMD is relatively most disturbed and Site REMU is most undisturbed).

Figure 4.5: Influence of clutch size on Minimum Permissible Distance

4.5 Clutch size, incubation period and nest success

4.5.1 Clutch size

A total of 845 eggs belonging to 277 nests were encountered and monitored in the two seasons

(2016/2017). During the 2016 breeding season, 493 eggs were recorded in 159 nests (82 at site

RELU, 69 at REMD and 8 at REMU), while 352 eggs were recorded in 118 nests (110 at site

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RELU, 7 at REMD and 1 at REMU) during the 2017 breeding season. The clutch size ranged from 1 – 4 (Plate 4.3- 4.10) in 2016 with a mean of 3.1±1.19, and in 2017, it was 1 – 5 eggs with a mean of 2.97±1.05 eggs. Only one nest was observed to contain 5 eggs Plate 4.7. Figure

4.6 shows the frequency distribution of clutch size.

Plate 4.3: Clutch size of 1 egg Plate 4.4: Clutch size of 2 Plate 4.5: Clutch size of 3 eggs eggs

Plate 4.6: Clutch size of 4 Plate 4.7: Clutch size of 5 eggs eggs

160 140 120 100 80 60 umberof nests

N 40 20 0 1 egg 2 egg 3 egg 4 egg 5 egg Number of eggs in the clutch

Figure 4.6: Frequency distribution of clutch size in Black-winged Stilt.

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4.5.2. Incubation period

A total of 33 nests were monitored from the time of laying of first egg till hatching (22 in 2016 and 11 in 2017). Only these nests were included in the calculation of the incubation period.

The incubation period ranged from 21 to 29 days. Figure 4. shows the frequencies of the incubation periods of nests monitored from the time of laying of first egg till hatching.

100.00% 100.00% 100.00% 90.00%

80.00% 87.50%

70.00% 75.00% 60.00%

50.00%

40.00%

umulative Frequency 30.00% 37.50% C

20.00% 25.00% 10.00% 12.50% 0.00% 0.00%15 22 23 24 27 28 29 33 Days

Figure 4.7: Cumulative frequency distribution of Black-winged Stilt incubation periods

4.5.3. Hatching success

Seventy-eight (78) nests representing 49% of total nests monitored were successful during the

2016 breeding season. In the 2017 breeding season 70 nests representing 59% of total nests monitored were successful. Hatching success per nest ranged from 1 egg hatching to 4 eggs hatching; the overall mean number of eggs hatching was 3.16 ± 1.01 (3.28 ± 1.03 for 2016 and

3.04 ± 0.98 for 2017). Table 4.1 summarises the number of nests and the mean hatching per clutch by clutch size for both breeding seasons. Table 4.1 summarises the fate of nests by clutch size for both breeding seasons. The only nest which was observed to contain 5 eggs failed

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(Table 4.2 and Table 4.3). The nests with a clutch of 4 eggs had a highest chance of an egg hatching for both years (65% and 71% for 2016 and 2017 respectively), followed by nests with

3 eggs for the 2017 breeding season (59%). Nests with a clutch of 3 eggs had less than 50% chance of hatching in 2016. Hatching success for nests with 2 and single eggs were 20%, 52% respectively for 2016 and 10%, 38% respectively for 2017.

Table 4.1. Number of nests, total number of eggs laid, eggs hatched and mean number of eggs hatched per clutch size. Year Clutch Number of Total number Number of Mean hatch ±SD size nests of eggs eggs hatched

2016 1 30 30 3 0.1 0.3

2 15 30 5 0.33 0.72

3 23 69 35 1.52 1.53

4 91 364 219 2.41 1.82

2017 1 16 16 6 0.38 0.5

2 17 34 18 1.06 1.03

3 39 117 65 1.76 1.16

4 45 180 124 2.76 1.80

5 1 5 0 0 0

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Table 4.2. Nest status by clutch size (Total number of eggs in brackets) 2016 2017

Clutch size/ Nest fate Freq % Clutch size/ Nest fate Freque % (Total uenc (Total ncy number of y number of nests) nests)

1(30) failed 27 90 1(16) failed 10 62.5

successful 3 10 successful 6 37.5

2(15) failed 12 80 2(17) failed 8fd 47.1

successful 3 20 successful 9 52.9

3(23) failed 12 52.2 3(39) failed 16 41.0

successful 11 47.8 successful 23 58.9

4(91) failed 30 32.9 4(45) failed 13 28.8

successful 61 67.0 successful 32 71.1

5(1) failed 1 100

During the 2016 breeding season, equal number of nests were successful as those that failed at sites RELU and REMU, whereas about 52% of nests at site REMD failed with about 48% being successful. In 2017, 40% of nests at site RELU failed, with 60% being successful; while at site

REMD, approximately 43% failed with 57% being successful. Only one nest was encountered at site REMU in 2017and it was not successful (Table 4.3).

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Table 4.3: Nest status at the sites for individual years Site 2016 2017

Nest fate Frequency % Nest fate Frequency %

RELU Failed 41 50 Failed 44 40

Successful 41 50 Successful 66 60

REMD Failed 36 52.17 Failed 3 42.86

Successful 33 47.83 Successful 4 57.14

REMU Failed 4 50 Failed 1 100

Successful 4 50 Successful

Eighty percent (80%) of 56 nests laid inside the salt pans were successful, while 47% of 221 nests laid on the dykes were successful. Nests without vegetation around them were more successful (55% of 211 nests) than nests with vegetation (48% of 67 nests) around them. Nests with water around them were more successful (54% of 269 nests) than nests without water

(50% of 8 nests) around them. Forty nine percent (49%) of 169 nests laid on the bare ground were successful, while 57% of 42 nests with pebbles as nest material were successful (Table

4.4).

Table 4.4: Factors influencing hatching success Factor (Total nests) Number successful (%) Number failed (%)

Nest position

Inside pan (56) 45 (80) 11 (20)

On dyke (221) 103 (47) 118 (53)

Presence of vegetation

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Absent (211) 117 (55) 94 (45)

Present (67) 31 (48) 35 (52)

Presence of water

Absent (8) 4 (50) 4 (50)

Present (269) 144 (54) 125 (46)

Nest material

Bare ground (169) 82 (49) 87 (51)

Pebbles (42) 24 (57) 18 (43)

Mud chips (27) 11 (41) 16 (59)

Feathers (5) 4 (80) 1 (20)

Grass (12) 5 (42) 7 (58)

4.5.4 Parental care

Black-winged Stilts showed parental care for their hatchlings, protecting them till fledging.

Immediately after hatching, Black-winged stilts removed the egg shells from the nest. They flew some distance to dispose of it. However, small shell fragments remained in the nest; which provided an indication that the eggs hatched. The chicks were able to move within two hours of hatching. Within a day or two of hatching, the hatchlings were escorted out of the nest site by the parents to a marshy swamp nearby.

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Several pairs were observed escorting their young away from the breeding sites (Plate 4.8).

This shows cooperation among parents after eggs have hatched and increases the chances of the young reaching fledging stage. Some of the parents flew above making high pitched noise when approached by an observer. This signaled that there might be young ones around.

Occasionally, when disturbed, parents would walk away from their chicks to take attention off the chicks. The minimum permissible distance was estimated to be 20 meters, beyond 20 meters, the birds flew very close towards the agent of disturbance attempting to strike with their wings.

A few days after observing the chicks being escorted, two chicks from the site where they hatched were seen in the vegetation in the swamp opposite the breeding sites. They took off immediately they became aware of the observer’s presence to the other side of the swamp which was inaccessible.

On one occasion during monitoring an egg was observed with cracks on the exterior. The egg hatched about 45 minutes later, within 30 minutes the chick’s feathers had dried and its feet were strong enough to move albeit wobbly. Within an hour the chick was agile enough to take off when it sensed the presence of the observer; it walked along the inner sides of the dyke and swam to the other side.

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Plate 4.8: Breeding pair escorting hatchling away from the site. (One parent leading the chick while the other exhibits aggressive behavior).

4.6. Biometric measurements of Black-winged Stilt eggs

The heights and widths of eggs encountered during the 2016 breeding season were measured, however during the 2017 season, egg weight was also recorded in addition to the height and w idth. For sites RELU and REMD, only eggs encountered on the dykes were measured because it was not possible to measure those in the pans. Measurements were taken for a total of 630 e ggs; 463 in 2017 and 167 eggs in 2017. The eggs ranged from 17g to 26g in weight, with a m ean of 19.71 ± 1.76g (Table 4.5). Figure 4.6 shows the frequency distribution of egg weights.

There was no difference in egg weight between the breeding sites (x2 = 0.12, df = 1, p-value =

0.72).

The mean egg height for the 2016 breeding season was 42.2 ± 3.1mm (range of 27.6 mm to 4

6.6 mm). In the 2017 breeding season, the mean egg height was 42.5 ± 1.65 (range of 38.1 m m and 47.0 mm). Figure 4.7 shows the frequency distribution of egg heights. There was no sig nificant difference in egg height between the two seasons (p-value=0.57) as well as between b reeding sites (x2=0.2, df=2, p-value=0.9).

Egg width varied from 18.6mm to 33.7mm, mean 30.5±1.86mm in 2016 and 27.5mm to 32.8 mm, mean 30.4±1.06mm in 2017. Figure 4.8 shows the frequency distribution of egg widths.

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There was no significant difference in egg width between the two breeding seasons (p-value

= 0.12), however, egg width differed significantly between the breeding sites (x2=7.43, df=2, p-value=0.02). Posthoc test (Bonferroni) revealed the difference occurred between Site REL

U and REMU (p-value=0.02).

Figure 4. shows the egg widths at the three breeding sites.

Out of the 463 eggs encountered during the 2016 breeding seasons, 225 were found at site

RELU, 213 at site REMD and 25 at site REMU. For the 2017 breeding season, 144 out of the total of 167 recorded were encountered at Site RELU, 21 eggs at site REMD and 2 eggs at site REMU.

Table 4.5 shows the distribution of egg measurements by egg number (order of laying). Egg height, width and weight decreased with order of laying, the first eggs laid were generally longer, wider and weighed more than subsequent eggs laid (

Figure 4.9 to Figure 4.11). The nest that had five eggs however showed exceptional behavior with height and width.

Table 4.5: Summary of egg measurements YEAR EGG MEAN ± SD MIN MAX N MEASUREMENT

2016 Height 42.1±3.17 27.6 46.6 463

Width 30.5±1.86 18 33.6 463

2017 Weight 19.71±1.76 17 26 167

Width 30.4±1.06 27.5 32.8 167

Height 42.5±1.65 38.1 47 167

N= number of observations; SD= Standard Deviation

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Table 4.6: Summary of egg measurements by order of laying

Order o N Egg height Egg width Egg weight f laying Mean ±SD Range Mean ±SD Range Mean ±SD Range 1 5 42.8 1.79 38.1-47 30.5 1.32 26-32.8 20.1 2.01 15-26 9 2 4 42.3 1.43 39.4-46.5 30.2 1.14 26.8-32.1 19.2 1.8 14-22 8 3 3 41.6 1.61 37.8-45.2 29.9 1.06 27.5-32 18.7 1.83 15-22 9 4 2 41.5 1.32 38.9-43.7 29.8 1.08 28.2-31.5 18.6 1.99 16-22 1 5 1 43 NA 43-43 29.7 NA 29.7-29.7 20 NA 20-20

N= number of observations; SD= Standard Deviation

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Figure 4.6: Histogram showing Figure 4.7: Histogram showing distribution of egg Figure 4.8: Histogram showing frequency frequency distribution of egg weights height distribution of egg widths

Figure 4.9: Relationship between Figure 4.10: Relationship between position of egg Figure 4.11: Relationship between position of position of egg in terms of order they in terms of order they were laid and egg weight egg in terms of order they were laid and egg were laid and egg height width

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Figure 4.12: Boxplots of egg widths at the different breeding sites

The data showed a significant positive correlation between egg weight and egg width (Figure

4.13). From the graph, egg weight increases as egg width increases. Figure 4.14 presents the correlation between egg weight and egg height and shows a positive relationship between egg weight and height. Comparing the correlation coefficient values for both correlations, egg width appears to be a better predictor of egg weight than egg height. Egg width accounts for

63% of the variability in egg weight while egg height accounts for 49% of this variability. Egg height also showed a positive relationship with egg width (Figure 4.15).

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Figure 4.13: Correlation between egg weight and egg width

Figure 4.14: Correlation between egg weight and egg height

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Figure 4.15: Correlation between egg height and egg width

4.7 Factors influencing nest success

The possible factors that could affect nest success and which were used in the model prediction were:

(i) distance of nest to road

(ii) distance of nest to closest nest

(iii) clutch size

(iv) egg height

(v) egg width

(vi) egg weight

(vii) minimum permissible distance

(viii) nesting site

(ix) nest location

(x) year

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(xi) presence or absence of vegetation

(xii) presence or absence of water.

Nest success was used as the response variable. Model selection was done using the stepwise backward selection with AIC value as selection criterion. Appendix 1 gives a summary of the models with individual variables and their AIC values. The table shows that clutch size has the lowest AIC value followed by nest location. Multivariate models and their AIC values are presented in Appendix 2.

The best fit model was

~ , = ( =′ ′) with AIC value of 317.15 and a McFadden r2 of 0.206.

A generalized linear model was fitted to test which variables best correlate with egg hatchability which was measured as the number of eggs hatched from each nest. All variables used in the binomial logistic model for nest success were imputed into the linear model.

Akaike’s Information Criterion (AIC) was used to select the best model using the backward selection procedure.

The best model was:

(ℎℎ ~ )

The best predictor for egg hatchability was clutch size (see Appendix 3). The second-best predictor was nest location. Since the AIC values for clutch size and nest location differ by more than 2, they are not considered equivalent. The variable year had a high AIC value and

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low r2 value, yet its presence in the model makes it more parsimonious; removing it from the model increases the AIC value and decreases the r2 value (See Appendix 4).

4.8 Causes of nest failure and chick mortality

The main factors responsible for nest failure were predation by dogs and flooding. Dog tracks were usually found near nests where a nest had been depredated (Plate 4.9). In some areas, the soil was very compact or had gravels and the dog tracks were not visible so the presence of shell fragments with spilled content, as well as scat (Plate 4.10 and

Plate 4.11) were used as an indication of predation. During a monitoring session, two dogs were observed roaming around the breeding sites. When they were driven away, several nests were discovered with freshly broken eggs and spilled content. This showed the destructive ability of domestic dogs on Black-winged Stilt nests.

Following rainy days, eggs were found in the water (

Plate 4.12) likely washed by the floods. In one instance a nest with one egg was by a crab hole. The crab had deposited mud from the hole onto the egg (

Plate 4.13). This caused the nest to be abandoned and eventually failed. A number of hatchlings were found dead in the water on the sides of the dykes (Plate 4.14). Cause of death appeared to be drowning, since no visual signs of injury were observed.

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Plate 4.9: Dog tracks found at Plate 4.10: Dog scat found Plate 4.11: Broken Black- near nesting area winged Stilt egg with spilled nesting area content

Plate 4.12: Egg washed from Plate 4.13: Nest and egg Plate 4.14: Drowned Black- nest due to flooding. covered by mud from crab winged Stilt chick hole

4.9. Runt eggs

A case of egg anomaly was encountered in a nest with two eggs; one egg was of normal size, but the other was abnormally small; a phenomenon known as “runt egg”. The smaller egg (runt egg) was the size of a Pratincole egg, but the shell pattern and coloration were that of a Black- winged stilt egg. The egg measured 27.6 x 22.5mm. The nest was however not successful as both had gone missing by the next visit to the field.

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4.10 Foraging Behavior

4.10.1. Diurnal time-activity budget

A total of 19,740 minutes of observations were made of the daily diurnal activity of Black- winged stilts at the Densu Delta Ramsar Site. The observations revealed that the Black-winged stilt spends about 51% of time foraging and the remaining 49% on resting, comfort activity and on other activities such as aggression, flying, chasing and vigilance (Figure 4.16). Figure 4.19 shows a 12-hour time activity budget of the Black winged stilt. The Black-winged stilt showed two peaks of foraging activity; first peak around 07:00 – 08:00 hours and a second around 16:00 – 17:00 hours.

5% 3%

Foraging Resting Comfort 41% 51% Others

Figure 4.16: Percentage of time spent on activity groups

100% 90% 80% 70% 60% Other 50% Comfort 40% Resting 30% Foraging 20% 10% 0% 06 00 07 00 08 00 09 00 10 00 11 00 12 00 13 00 14 00 15 00 16 00 17 00 Total Figure 4.17: Diurnal time-activity budget of the Black-winged stilt

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Figure 4.418 shows a monthly pattern in activity rhythm of Black-winged stilts. About 55% of the time was spent foraging and 45% spent resting in November. In December, about 67% of time was used to forage, 24% resting, 6.5% on comfort activities and about 2% on other activities. The time spent foraging did not vary by much in January (69%), the amount of time spent resting also increased to 28%. The Black-winged stilts spent 60% of the time foraging in

February and 21% resting. The lowest amount of time spent foraging was recorded in March

(47%). In April, about 54% of the time was spent on foraging activity.

The breeding period for Black-winged Stilts in Ghana was from March to July. During the breeding season, Black-winged Stilts spent on average 41% of the time foraging, 11% resting and 46% on reproductive activity (nesting and brooding) (Figure 4.19).

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100% 90% 80% 70% 60% Other 50% Comfort 40% Resting 30% Foraging 20% 10% 0% NOVEMBER DECEMBER JANUARY FEBRUARY MARCH APRIL

Figure 4.18: Variations in the diurnal activity patterns of Black-winged stilts in the months studied

Foraging Resting 46% 41% Comfort Other Reproduction

11%0%2%

Figure 4.19: Activity budget of Black-winged Stilts during the Breeding period

Black-winged Stilts displayed different activity rhythms at the various study (Figure 4.20).

Forty-five percent (45%) of the time was spent foraging at the relatively undisturbed breeding

Site (RELU), 69% at the most disturbed breeding site (REMD), 60% at the Estuary breeding site (REMU), 61% at Foraging site 1(FORS1), and 76% at the Foraging site 2 (FORS2). The highest percent of resting activity was 39% at site RELU and the lowest of 14% at FORS2. At

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the roost, 98% of the time was spent roosting, with the remaining 2% of the time spent on other activities.

100% 90% 80% 70% Other 60% Reproduction 50% Comfort 40% Resting 30% 20% Foraging 10% 0% BREED A BREED C ESTUARY FORAGE 1 FORAGE 2 ROOST

Figure 4.20: Variations in diurnal activity patterns of Black-winged stilts at various study sites

Aside the three main sites where foraging behavior was studied, foraging Black-winged Stilts were also observed feeding in diverse habitats from areas with open water to areas with vegetation where they could hide in the grass. Roosting Black-winged Stilts showed a preference for areas of open shallow water where they have a clear view of their surroundings and thus can spot possible threats early enough. Roosting birds aggregated densely at the roosting sites. Black-winged Stilts roosted in mixed flocks with Eurasian Curlews (Numenus arquata), Whimbrels (Numenius phaeopus) and Little Ringed Plovers (Charadrius dubius).

4.10.2 Prey of Black-winged Stilt and densities of macroinvertebrate

Black-winged Stilts were observed feeding at a variety of habitats, both on dry land and in water of varying depths. It was not possible to tell exactly what they fed on. However, still images obtained from video playback revealed small fishes likely to be juvenile fish (Plate

4.15).

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The benthic macroinvertebrate community at the estuary was dominated by polychaetes (Class:

Polychaeta) accounting for about 99.0% of all macroinvertebrates in benthic samples and

Hastula sp. (Class: Gastropoda) accounting for 1% of macroinvertebrates. No living macroinvertebrate was found at the site sampled within the core wetland, although Black- winged Stilts were observed foraging prior to sampling. Samples from the core wetland were dominated by shells embedded in thick layers of algal mats.

The densities of macroinvertebrates encountered were computed for each station at the estuary.

Appendix 5 shows the densities of macroinvertebrates found at the different sampling stations at the estuary and the distribution of macroinvertebrates across the sediment profile (top 5cm and bottom 10cm) (Figure 4.21). Majority of macroinvertebrates occurred within the top 5cm

(86%) with a small proportion (14%) occurring within the bottom 10cm of the core samples taken, indicating that the majority of macroinvertebrates were available to foraging birds, particularly the Black-winged Stilt at the estuary.

Plate 4.15: Foraging Black-winged Stilt with prey item between bill.

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Figure 4.21: Proportion of Macroinvertebrates sampled that occurred within the top 5cm and bottom 10cm. (This is based on densities calculated per m3 from the numbers of items collected during sampling).

4.10.3. Black-winged stilt foraging behavior

Black-winged stilts at the Densu Delta Ramsar wetland were observed foraging singly, in pairs or in loose flocks, on land and in water, sometimes to a depth almost deeper than the length of their tarsus and tibia. At certain areas, Black-winged stilts shuffled between foraging on land and in the water; they moved between the two several times while feeding opportunistically.

Foraging Black-winged stilts were observed to tolerate other species and foraged in mixed flocks with herons, egrets and other waders like the sanderling (Calidris alba), common ringed plover (Charadrius hiaticula), Whimbrel (Numenius phaeopus), eurasian curlew (Numenius arquata) and the common moorhen (Gallinula chloropus) (

Plate 4.16). During the study period, the only aggressive behaviour exhibited while foraging was observed to be targeted towards intruders such as the pied crow (Corvus albus) and the yellow-billed kite. In many cases, the pied crows and kites swooped down very close to the foraging flock, but there was no response from the Black-winged stilts. This was observed mostly when the Black-winged stilts foraged in mixed flocks with herons and egrets, sometimes small flocks and individuals flew off to different locations.

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Plate 4.16: Black-winged Stilts in a mixed flock with some other birds

Black-winged stilts were observed moving in groups in a line and using the same feeding style, usually probing or plunging. Aggression while foraging was generally low and no case of kleptoparasitism was observed among Black-winged stilts and between Black-winged Stilts and other species.

The mean distance allowed between a foraging Black-winged Stilt and other foraging Black- winged Stilts was 0.58 ± 1.19 m. Individuals feeding alone were not included in the analysis.

The mean distance allowed between a foraging Black-winged Stilt and other species was 0.73

± 1.18 m. Here again, individuals who were observed foraging alone were taken out of the computation.

There was no significant difference in the mean inter- and intra-specific foraging distances

(W=733.5, p-value = 0.18). Kruskal-Wallis test for relationship showed significant difference in intraspecific foraging distances at the three foraging sites (x2=8.8345, p-value = 0.01207).

A post hoc test using the Bonferroni method revealed no significant differences between foraging site FORS1 and foraging site FORS2 (p-value=0.21) and between foraging site

FORS1 and ESTF (p-value=0.052). However, there was significant difference between FORS2

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and ESTF (p-value =0.003) (see Figure 4.22). Kruskal-Wallis test showed no significant association (H=1.4033, p-value=0.50) in the distance between foraging Black-winged Stilts and birds of other species at the three foraging sites (Figure 4.23).

Figure 4.22: Nearest neighbour distance of foraging Black-winged Stilts to Conspecifics at the foraging sites

Figure 4.23: Nearest neighbour distance of foraging Black-winged Stilts to other species among the foraging sites

The depth of water (as measured in relation to leg length) in which birds foraged varied between

0-16 cm, with mean and median values of 7.8 cm and 9 cm respectively. There was a significant difference in the water depth used at the three sites (H = 12.62 and p – value = 0.002).

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Bonferroni test showed that no significant difference (p-value = 0.46) exist between water depth selected for foraging at foraging sites FORS1 and FORS2, but there were differences between FORS1and ESTF (p-value=0.01) and FORS2 and ESTF (p-value=0.0009). Figure

4.24 shows the water depth within which Black-winged stilts foraged at the three foraging sites.

Adult birds appeared to forage in deeper waters than juvenile birds (W=259, p-value=0.001, confidence interval=5.0-10.9). Figure 4.25 shows the depths of water juveniles and adults preferred to forage in.

Figure 4.24: Depths in which Black-winged Stilts foraged at the foraging sites. (Number of observations = 59)

Figure 4.25: Depth of water in which juvenile and adult Black-winged Stilts foraged

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4.2.4. Foraging style

Black-winged Stilts were observed using five foraging styles; pecking, probing, scything, filtering and plunging. Plunging was the most used foraging style used by black-winged stilts counting for 39% of observations made, followed by probing (29%) and pecking (20%).

Scything and filtering were the least used accounting for 11% and 1% of all observations respectively (Figure 4.26).

Figure 4.26: Frequency of use of feeding styles.

4.2.5. Feeding rates

Feeding rates were estimated as the number of attempts per minute of each feeding technique.

Median pecking rate was 2.87 pecks per minute. Pecking rate did not vary across the three sites

(x2=0.7, p-value=0.69).

Median probing rate was 2.87 probes/min. Kruskal-Wallis test reveals differences (x2=10.743, p-value=0.0046) in probing rate at the various sites. Post-hoc test reveals that the difference occurs between FORS1 and FORS2 (p-value = 0.028) and FORS1 and ESTF (p-value=0.001).

Probing rate did not differ significantly between FORS2 and ESTF (p-value = 0.4) (Figure

4.27).

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Figure 4.27: Boxplots of probing rates across the three foraging sites.

There were no significant differences in scything rates across the sites at α=0.05 (x2=4.84, p- value=0.08). However, sites FORS1 and FORS2 differed significantly when post-hoc test was applied (p-value=0.02) (Figure 4.). Filtering rate did not differ significantly between the sites

(x2=0.48, p-value=0.79) (Figure 4.). The rate of plunging across the three foraging sites differed significantly (x2=8.7861, p-value=0.012). However, the difference in medians occurred only between FORS1 and ESTF and FORS2 and ESTF with p-values of 0.015 and 0.010 respectively. Figure 4. shows the plunging rates across the three sites.

Figure 4.28: Boxplots of Scything rates at the three sites

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Figure 4.29: Boxplots of Filtering rates at the three sites.

Figure 4.30: Boxplots of Plunging rate at the three foraging sites.

Intake rate percentage (computed as the ratio of the number of successful feeding attempts to the total number of feeding attempts expressed as a percentage) averaged 32%, and varied acr oss the three sites (x2= 27.086, df = 2, p-value <0.0001). Intake rate did not differ between F

ORS1 and FORS2 (p-value=0.35), but differed between FORS1 and ESTF (p-value<0.0001), and FORS2 and ESTF (p-value<0.0001). Figure 4.31 shows the difference in medians of inta ke rate at the three foraging sites with FORS2 having the highest intake rate of the three sites.

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Figure 4.31: Boxplots of Intake rates across the three foraging sites

100

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CHAPTER FIVE

5.0 Discussion

5.1. Breeding ecology

5.1.2. Nesting behavior of Black-winged Stilts

Black-winged Stilts started nesting early March in 2016 and early April in 2017. This is similar to the breeding period of Black-winged Stilts in Spain which has been reported to be between

March and May by Cuervo (2005). Ashoori (2011) reported that Black-winged Stilts built nests from 28 April and 10 May 2015 in 22 Bahman Wetland in Boujagh National Park, Northern

Iran. The onset of nest construction reported by Ashoori (2011) is relatively later than what was observed in this study and Cuervo’s study. This could be due to geographic differences and differences in climatic conditions. Findings from (Barati et al., 2012a) showed that egg laying occurred between 16 May and 8 June in Western Iran. Their results contrast with that of

Ashoori (2011) probably due to differences in microclimate as their study was conducted in

Western Iran. Nesting period reported by Barati et al. (2012a) also contrasts with results from this study as well as Cuervo (2005).

It was observed that during 2016, the rains in Ghana commenced early but delayed in 2017, which resulted in a corresponding delay in the commencement of egg laying. It appears that rainfall provides a cue for the commencement of nesting and egg laying. This may be because of the increase in food availability and abundance after the rains. According to Barshep et al.

(2011), egg laying in the Curlew sandpiper is delayed if cold weather limits the abundance of surface arthropods when the birds arrive at their breeding areas or if the grounds are still covered by snow. They further indicate that the delay in the onset of breeding consequently delays post-breeding migration. Adamou et al. (2009) report that Black-winged Stilts in

Senegal started egg laying when temperatures increased to 15℃. They noted that the water

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level in the wetland where they conducted the study was independent of rainfall. However, unlike this study they did not observe significant differences in egg laying dates across the three years of study and attributed this occurrence to the relative consistency in weather conditions.

Rainfall was the main source of water at the Densu Delta breeding sites. Rainfall causes inundation of the pans and creates an ideal environment for both micro and macro-invertebrates that are food items for Black-winged Stilts. Thus, Black-winged Stilts either advance or delay their egg laying date to coincide with the rains and consequent inundation of the sites so that there will be food close to their nests. This way they do not go far to forage and both male and female parents can remain close to brood, to shelter, defend and protect the nest (Ueng et al.,

2009). In this case, the chicks also obtain food readily in the breeding sites right after hatching rather than having to move away from the site in search of food or depending on the parents for food. Pierce (1996) reports that even though breeding Black-winged stilts nested in areas either close or far from their feeding grounds, when food is available, they nest at the feeding areas, which usually is a flood-prone riverbed. In this case there is a tradeoff between nest losses from floods and food availability. Black Stilts (Himantopus novaezelandiae), which are in the same family as the Black-winged Stilt also chose breeding sites that were close to areas where they could forage according to Pierce (1996).

Black-winged Stilts constructed their nests mainly in the mornings especially for nests that were depressions on the bare ground. This is because the soil was softer in the early morning because of dew but hardened later in the day when the sun came up, making it more difficult for the birds to scrape the soil.

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Black-winged Stilt eggs are cryptic with spotty coloration. This could be why majority (61%) of nests were shallow depressions on bareground. This is probably to reduce the risk of predation as the egg pigmentation blends with the ground making it difficult to locate. Götmark

(1993) found that avian families with large conspicuous nests tend to have noncryptic eggs while families with small ground nests or nest scrapes have eggs that match the background

[obtained from (Westmoreland, 2008)]. Westmoreland & Best (1986) mentioned that egg coloration evolved in egg laying generally for two functions; thermoregulation and as an antipredatory strategy. Bakken et al. 1978) found that particular pigments used for egg coloration minimize heat absorption from direct insolation. Plain colored white eggs are reflective and thus bounce off heat. They further explain that during the evolution of egg coloration, selection due to predation appears to favor pigmentation while selection resulting from solar heating opposes pigmentation. Black-winged Stilt’s cryptic eggs may have thus evolved in response to predation. The threat of overheating from solar radiation is minimized if not completely eliminated through brooding. Tinbergen et al. (1962) in an experiment placed cryptic and white eggs in meadows visited by avian predators and found that the cryptic eggs suffered less predation. A later field experiment by Westmoreland & Best (1986) where plain white eggs were painted also reported a greater number of cryptic eggs surviving than white eggs.

However, during their study some painted cryptic eggs were abandoned by the parents after they were painted. Nevertheless, those that were not abandoned saw higher survival than white eggs. However, Karel (2001) reports that there was no significant effect of egg colour on nest survival in the Song thrush (Turdus philomelos).

Twenty-three percent (23%) of the Black-winged Stilt nests had pebbles as nest material; these were nests in the salt pans. The pebbles provided a solid platform for the nest and they were in readily available throughout the sites. It is likely that pebbles were also used for the nests in

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the pans because they provided the nest some amount of porosity that allowed water to pass in between without dislodging them, especially in the case of rainfall, the nest was firm and was not washed away by the flowing water. Ten percent (10%) of nests were on mud chips. The color of the dried chips of mud also offered camouflage for the eggs as the pigmentation of the eggs blended in. Only 4% of the nests had grass as nest material and 2% had feathers as nest material. This is probably because these items make the nest conspicuous and prone to predation as they usually contrast with the surrounding soil.

Some of the nests that had grass as nest material were laid in grass patches and thus were hidden from observers. Even at close proximity, it was difficult to spot these nests. This makes grass ideal for constructing nests but there were very little grass patches at the breeding sites; thus only a few nests were constructed this way. Barati et al. (2012) contrasted the breeding ecologies of the Black-winged Stilt and the Gull-billed terns and report that Black-winged Stilts preferred areas of lower plant density especially sandy beds, this is similar to what was observed in this study. They further report that unlike the Black-winged Stilt, the Gull-billed

Terns preferred higher plant density areas and that they achieved increased clutch size, brood size and hatching success with increasing plant density.

Barati et al. (2012) speculate that nest structure actually depends on characteristics of the location and the availability of nesting materials. As much as this assertion is true, it does not capture the evolutionary importance of nest construction and nest material selection. For instance, in this study, some nests were just scrapes on the bare ground with hardly any nest material despite the abundance of nest material such as feathers, plant material and dried mud chips, which were used by other breeders, at the nesting area. Some nests without any nest material were situated very close to other nests that had nest materials. Even some nests found

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in the grass patches had extra materials in them while others had less material though they were all found close by. These lend to the argument that camouflage is an important factor in selection of nest material and subsequently nest structure.

Karel (2001) observes that visually searching predators may first spot the nest or the adult bird but not the eggs. This is probably why majority of Black-winged Stilt laid eggs on the bare ground so that when not attended they would not be conspicuous to avian predators. As regards the presence of the adult bird as a cue for predators, Black-winged Stilts defend their nests using aggressive displays. Brennan (2010) also found that the risk of predation of the Great

Tinamou (Tinamus major) was higher during the incubation period when the eggs were covered by the parent than during the egg laying period when they were exposed, suggesting that predators use the presence of incubating adults to locate the clutch.

With the exception of the few nests discovered at the flat land adjacent a mudflat, all other nests were either in the pan on mounds or on the dykes. In 2016, 154 nests were found on the dykes and 5 in the pan while in 2017, 67 were found on the dykes and 51 in the pans. The ratio of nests discovered on the dykes to those discovered in the pan differs between the two years.

It is likely that those that constructed their nests and laid eggs on land did so to avoid flooding from rains when the pans got full. It may be also safe to assume that those that nested in the water did so to escape predation by domestic dogs or other land animals. Experiences of nest loss due to the floods may have caused some birds to construct nests on the high dykes. Cuervo

(2005) points out that Black-winged stilts are better adapted to nest close to water. Barati et al.

(2012) indicates that Black-winged Stilts nested close to water because they may have developed mechanisms to minimize reproductive failure from flooding. It was also observed

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that for nests in the salt pans, even after nest construction and laying of eggs, the breeding pairs kept adding material to the nest till hatching, this provided a wider base and support for the nest. There appears to be a tradeoff in the exact location to build a nest. Either Black-winged

Stilts nested in the pan and risk exposure to floods or on the dyke and risk predation by the dogs. Pierce (1996) observed that Black-winged Stilts nested in flood-prone riverbeds when there was food available. Barati et al. (2012) indicate that although there were no nests closer than 0.6 m to the water, by far the majority (74%) were within 3 m of the water’s edge, with only small numbers up to 20 m.”

Distance to road varied between the sites. The relatively undisturbed site had the widest range of nest distance to the road followed by the most disturbed site and then the relatively most undisturbed site. The relatively undisturbed site is where the breeding pairs commenced nesting. At the beginning of the breeding season, nests were scattered throughout the site and were closer to the road. Most of these nests were destroyed or depredated. Nests laid later were situated further from the road. All nests were however very close to the water, either in the pans or on the dykes. Breeding started later at the most disturbed site after the salt pans were inundated with water. Barati et al. (2012) report that “greater distance from water might reduce breeding success when water levels subside during the breeding season leading to mortality during egg and chick rearing period”. At the relatively most undisturbed site, nests were closer to the road (pathways) in the grass. There was no difference in distance to nearest nest between the sites basically because the species showed the same behavior across the sites and aggregated around water as has been reported by Cuervo (2004); Goriup (1982); and Pierce

(1986). Majority of the nests were within 40m of each other, offering protection against intruders through mob action (Göransson et al., 1975).

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Copulation behavior observed for Black-winged Stilt in this study is similar to observations made by Goriup (1982); the female initiated mating. The same behavior has been described by

Hamilton, (1975) for the Avocet, in the same family (Recurvirostridae) as the Black-winged

Stilt. Goriup (1982) reports that copulation lasted about one minute, for the single observation in this study, it lasted a few seconds longer (one minute 13 seconds). In the description by

Goriup (1982) of the Black-winged Stilt mating behavior, after cloacal contact, the male covered the female with his wing, but this did not occur during the observation made in this study. Studies have shown that mating occurs several times before egg laying and it increases till clutch completion (Tasker & Mills, 1981; Pierce, 1986; Marchant & Higgins, 1996).

Marchant & Higgins (1996) indicate that for the Black Stilt which exhibits similar copulation behavior as the Black-winged Stilt, copulation bouts last on average 80 seconds. They also mention that a maximum of 7 copulation bouts were observed per breeding pair per day and that copulation peaks before laying and stops 2-3 days after start of laying or continues until the last egg. Tasker & Mills (1981) report that copulation mounts in the Red-billed Gull (Larus novaehollandiae scopulinus) occurred quite early but became more frequent about 30 days to egg laying. They indicate that a peak was reached 3 days to egg laying and dropped after clutch completion.

Black-winged Stilt breeding pairs took turns brooding the nest throughout the day. Similar behavior has been observed in the Black Stilt (Marchant & Higgins, 1996). Because the birds were not marked, it is not possible to determine whether the pair spent equal time at the nest or which individual spent more time brooding or attending to the nest. Cuervo (2003) however, reports that both parents invest equal time and effort in nest attendance. Marchant & Higgins

(1996) on the other hand indicated that for the Black Stilts, the male did most of the incubating for the first 5 days. Reports for the Black-winged Stilt show that incubation commences after

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clutch completion (Cuervo, 2003; Cuervo, 2005; Yeates, 1938). Biparental care has been observed in waterbirds especially those that breed in tropical hot environment (Alrashidi et al.,

2010; Kosztolányi et al., 2009). According to Kosztolányi et al., (2009), “the high frequency of biparental care suggests that an extreme environment, such as in the Arabian Desert, may favour shared brood care” and also chicks should constantly be brooded and shaded to avoid overheating, hence nest attendance, if performed by both parents, is an effective way to ensure chick survival.

During the hatching period, aggressive behaviour was very intense so that even other waders were not permitted near the nests. A little tern (Sterna albifrons) was intercepted and knocked into the pan containing water. The aggression was intense during this period because the safety of the chicks was at stake. As reported by Goriup (1982) Black-winged Stilt chicks were able to move from the nest and fend for themselves within an hour of hatching. The fledging period could not be monitored in this study because Black-winged Stilt chicks were led away from the breeding site shortly after hatching. Some chicks were observed in a swamp opposite the breeding sites but the nature of the swamp prevented further observation of the chicks.

The mean incubation period recorded in this study was 23 days during the study. Cuervo (2005) reported a mean incubation period of 22 days while Boekel (2016) reported 28 days. The similarity and difference here could be attributed to ambient temperature. Ghana and Spain have similar temperature gradient while Netherlands is cooler. The length of incubation is shorter in tropical regions while colder regions have longer incubation periods. Breeding Pairs in the Netherlands need to brood for longer and provide more heat to keep eggs at optimal temperature, whereas in the tropics, brooding times will be shorter and would be employed to both keep the eggs warm during the evenings and cold days as well as shield the eggs from

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overheating and desiccation when temperatures are high. Generally, less heat would be required from the parents for brooding in the tropics than in temperate regions such as the

Netherlands.

Immediately after an egg hatched the parent removed the egg shells from the nest. This behavior has been recorded in a variety of species including the Black Stilt (Marchant &

Higgins, 1996); the Black-Headed Gull, Larus ridibundus L (Tinbergen et al., 1962);

Semipalmated Sandpipers, Calidris pusilla, (Sandercock, 1996); and Black-necked Stilts,

Himantopus mexicanus, and American Avocet, Recurvirostra avosetta (Sordahl, 1994).

Tinbergen et al. (1962) postulated a number of theories explaining why birds removed shells from the nest after eggs hatched. These include preventing injury from sharp edges of the shells to chicks; preventing bacterial infection, preventing attraction of aerial predators, preventing shells from interfering with brooding; and preventing egg capping. The reason behind egg shell removal for Black-winged Stilts was probably to prevent the shells from attracting aerial predators and also to prevent egg capping which was observed once in this study. The instance of egg capping observed prevented the egg that was capped from hatching.

The clutch size recorded during the study ranged between 1-5 eggs per nest. Similar clutch sizes have been reported by Cuervo (2003) and Ashoori (2011). Ashoori, (2011) attributed the occurrence of 5 eggs in a nest to the quality of the habitat. Elmalki et al. (2013) report clutch size of Black-winged Stilts in Morocco ranging between 3-4 eggs. For Gholami et al. (2017)

100% of 12 nests monitored contained 4 eggs. Egg measurements recorded by Gholami et al.

(2017) were 41.9 ± 0.6mm, 29mm and 12 ± 0.07g for egg length, width and weight respectively for a total of 48 eggs. The mean egg measurements reported by Gholami et al. (2017) did not differ from measurements recorded in this study however, the maximum length (43mm)

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recorded was lower than the maximum length (46mm) recorded in the current study. The minimum egg length was however smaller in this study than what Gholami recorded, but it was due to the occurrence of a runt egg. Elmalki et al. (2013) report mean egg measurements for

Black-winged Stilts in Morocco as follows: length: 43.98±0.16 and width: 31.25±0.16. These also did not differ much from measurements recorded in this study. Elmalki et al. (2013) note also that egg measurements did not differ across time.

It is however, interesting to note that only one nest containing 5 eggs was encountered during this study which was the same for Ashoori’s study in Northern Iran (Ashoori, 2011). Egg widths and heights did not differ significantly between the two years in this study probably because conditions at the sites did not change in terms of available resources such as food.

Adamou et al. (2009) however, observed that mass, length, breadth and volume of Black- winged Stilt eggs at a natural desert oasis wetland in Algeria tended to decrease over a three- year period (2004 to 2007), which they attributed to declining hydrological conditions at their study site.

Two runt eggs were encountered during the study, once each year. The occurrence of runt eggs is not a new phenomenon and has been recorded by egg collectors since the 1800’s; one of the earliest reports was by Jacobs (1898). Prior to that many collectors had encountered it but it had not been documented. Mallory et al. (2004), report that runt eggs occur in clutches of a wide variety of avian species. Their study of runt eggs in wild nesting ducks, geese and swans revealed 215 out of 551,632 (0.039%) eggs to be runt eggs. They indicate that “cavity nesting waterfowl had lower incidence of runt eggs than ground nesting waterfowl”.

5.1.2. Hatching success and factors affecting hatching success

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During the 2016 and 2017 breeding seasons, hatching success was 49% and 59% respectively.

Toral & Figuerola (2012) recorded a nest success of 50% (using the Mayfield method) for the

Black-winged Stilt in Spain. Cuervo, (2004) report a low hatching success of 31% (N=29) in

South Western Spain. Elmalki et al. (2013) report 41.9% hatching success in Morocco which is lower than what was recorded in this study.

The difference in nest success between the two breeding seasons could be due to differences in the levels of disturbance between the two years. It has been reported that early breeding pairs experience greater nest failure that later nesting pairs (Pierce, 1986). During the 2016 breeding period, nesting and egg laying started earlier than 2017, also it was observed that almost all the nests that were initiated very early failed. Pierce (1986) postulates that early nesting pairs face high predation risk as a result of low food availability during that period. On the contrary,

Cuervo (2005) reports that hatching success was generally highest in early nests and lowest in late nests and did not differ significantly among early, intermediate and late nests.

The results show that the higher the number of eggs in a nest the higher the chance of success.

This could be due to the fact that parents are less likely to abandon nests with more eggs than nests with fewer eggs. Cuervo (2005) states that “it is probable that birds abandon their nests more easily in the case of disturbance when only one or few eggs have been laid. As the clutch is completed, clutch value increases and adults would be more reluctant to desert nests”. Also by the time the second egg in the clutch is laid the male would have started brooding so is present to defend the nest (Cuervo, 2003; Marchant & Higgins, 1996).

Out of the thirteen variables tested for association with nest success, five showed significant correlation. These are: the number of eggs found in the nest at first sighting; clutch size of nest;

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nest location; distance of nest to road; and distance of nest to nearest nest. For some of the nests egg laying was advanced before the nest was discovered, it is likely that some of these nests, if not all, were nearing clutch completion when they were. Nest location has been shown to influence nest success of stilts in relation to predation risk (Pierce, 1986). Pierce (1986) reported that distance of a nest from the centre of the colony influenced nest success as nests closer to the centre of the colony experienced less predation.

The distance to road and distance to closest nest were significant factors that influenced nest success. During aerial attacks by crows and kites, Black-winged Stilts at nearby nests attacked the intruders together, therefore the distance of a nest to the closest nest determines how it benefits from mob action in warding off intruders (Göransson et al., 1975). This is supported by Pierce’s comparison of susceptibility to predation between the Pied Stilt (Himantopus himantopus leucocephalus), an Australian race of the Black-winged Stilt (Himantopus himantopus) and Black Stilt (Himantopus npvaezealandiae) where he found that Black Stilts had a lower breeding success of 1% compared to the 8% of Pied stilts and attributed this difference to the breeding habit of Black Stilts which nested along stream banks that were often frequented by predators while Pied Stilts nested in swamps that were not predators were few.

The factors that influence the number of eggs that hatch were clutch size, nest location, presence of vegetation and distance to road. Despite the fact that nest success differed between the years, the variable “years” wasn’t a significant factor in the parsimonious model for whether a nest was successful or not, however, it was important in determining how many eggs hatched.

Cuervo (2005) points out that “hatching success varies enormously by year and locality, ranging from almost complete breeding failure to 88% success.”

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The main causes of nest failure observed were flooding and predation by dogs. Some eggs were observed with punctures on the outside, likely to have been caused by a predator (bird of prey). Most nest failures by predation occurred earlier in the breeding season, as Pierce (1986) points out, this could be due to the absence of alternative sources of prey for predators at the beginning of the breeding season. Barati et al. (2012) in comparing the reproductive ecologies of Black-winged Stilts at two colonies in West Iran observed that hatching success was lower at one of the colonies AghGol and attributed this to a decline in water level which made the colony accessible to grazing animals that trampled the eggs, as well as nest predators. In his study on nest-site selection and characteristics in Avocets and Black-winged Stilts in Spain

Cuervo, (2004) report that 15 out of 29 nests were flooded and 5 depredated, and that all nests with depredated clutches contained egg shell fragments with rat Rattus spp teeth marks. Cuervo mentions that the rats lived on the island and predated preferentially on nests close to the island as they are able to reach the nest by walking on the dykes.

5.2. Foraging Behavior

5.2.1. Diurnal activity patterns

From a total of 19740 minutes of observations, Black-winged Stilts spent majority (51%) of their time on foraging activity. Ntiamoa-Baidu et al. (1998) report various percentages of day time spent on foraging by different species of waterbirds. The amount of time spent foraging has been reported to have a positive correlation with body size (Nol et al., 2014) and guild

(Ntiamoa-Baidu et al., 1998). Ntiamoa-Baidu et al. (1998) reported that species feeding on small prey spent a lot more of the daytime (mean 66%) foraging than fish eating species (37%), and that predominantly social foraging species spent a lot less (35%) of the daytime foraging compared to non-social foragers (63%). Some reasons proposed for smaller birds spending

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more time foraging include; (i) they have smaller capacity to hold food and thus have to forage continuously; (ii) they also can only take small prey items; which (iii) are low in caloric content;

(iv) they show little selection for prey and continue feeding the entire day with short breaks in between (Nol et al., 2014). Larger birds thus spend less time foraging by obtaining larger prey items of higher caloric value (Nol et al., 2014) and spend the rest of the time resting while they digest the food eaten. Based on this, it is not unusual that the Black-winged stilt being a medium size bird spends about half the daytime foraging.

Black-winged stilts showed two feeding peaks; one early in the morning at 7 am and the second one around 4pm. This daily pattern is similar to results obtained by Ntiamoa-Baidu et al. (1998) for the Black-winged stilt and is characteristic of many wader species. The first peak in the morning could be due to hunger after roosting overnight. The amount of time spent feeding reduced till it reached lowest point around 1pm. This is when ambient temperatures were highest. The birds thus rest during this period to avoid exertion and over-heating.

The second foraging peak occurred right before dusk. The Black-winged Stilt has however been observed to forage at night (Goriup, 1982; Ntiamoa-Baidu et al., 1998). Goriup (1982) observed that Black-winged Stilts foraging at night use audible rather than visual cues to detect prey, which is reasonable considering that visibility is low at night.

Black-winged Stilts spent about 41% of the day time resting. The proportion of the flock resting was highest during the afternoon (13:00), mainly because ambient temperatures were high.

While larger birds foraged less and rested more (Nol et al., 2014), medium sized birds like the

Black-winged Stilt use about half of the daytime resting as was observed in this study. Comfort activity took up 5% of the day time of the Black-winged Stilt and was more frequent during the early hours of the day and at dusk. Ntiamoa-Baidu et al. (1998) reported that only a small

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fraction of the daytime (average 10% for 25 wader species including Black-winged Stilt) was spent on comfort activities and Nol et al. (2014) also report that non-breeding birds spent less time on maintenance (comfort). During this study, about 10% of the time was spent preening between 6:00 and 8:00 and around 16:00, the peak foraging periods. Bathing was also observed to be high during the first foraging peak (7:00) but not during the second peak.

Nol et al. (2014) report that foraging birds spent the majority of their time foraging and a small amount of time on locomotion that is not related to foraging. During the current study, Black- winged Stilts were observed moving from site to site within the wetland but spent very little time (<1%) on this activity, similar to findings of Nol et al. (2014). Their movements were mainly from one foraging site to another to continue feeding or from foraging site to roost and vice versa. The movements correlated with time of day and water level. Ntiamoa-Baidu et al.

(1998) indicated that waterbirds spent a small proportion of their time commuting between roosts and feeding areas. In this study, it was observed that during periods of low feeding activity, Black-winged Stilts flew to roost sites to rest. These periods usually coincided with the high tide, high water level and high ambient temperature. Roosts were observed to hold larger flocks than the individual foraging sites, indicating that Black-winged Stilts used communal roosts.

Vigilance activity was carried out by all individuals especially during the breeding periods and when individuals foraged alone. When Black-winged Stilts foraged in a flock very little time was allocated to vigilance. This may be because with more eyes, predators or sources of disturbance can be detected easily and earlier than when there is just a pair of eyes. Black- winged Stilts would rather move to alternative foraging areas than spend energy defending the current sites (Goss-Custard et al., 2006). Some studies have indicated that waterbirds spend a

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small fraction of the time on activities such as aggressive behavior and predator avoidance

(Ntiamoa-Baidu et al., 1998; Nol et al., 2014). Nol et al. (2014) also report that only a small portion of the time was spent on aggressive behavior. Aggression or competitive interaction were not observed, likely because the sites had enough food and Black-winged Stilts would rather move away and continue feeding than to waste time and energy competing for food which was abundant.

5.2.2. Foraging habitats and water depth selection

Results from the macroinvertebrate survey show that prey occurred in patches at the Estuary site with higher concentrations in the top 5cm (86%). However, few Black-winged Stilts were observed foraging at the estuary site despite the prey availability. This may be due to the very dynamic nature of the water regime at the site. They may choose to forage at the other sites where the water regime is less dynamic than to forage at the estuary. Also, at the estuary, even though at some time during the study, benthic prey density was fairly high and within reach, they were only available during low tide when the water level had dropped considerably. In addition, other species with longer bills such as the whimbrels and curlews may be more equipped to utilize benthic organisms at the estuary than the Black-winged Stilt, thus the low numbers of Black-winged Stilts foraging at the site (Choi et al., 2017). Choi et al. (2017) indicate that female Bar-tailed godwits have longer bills than males allowing them to reach deeper when feeding on polychaetes. The presence of the longer billed birds at the estuary posed as competition for the Black-winged Stilts and thus Black-winged Stilts tended to avoid the estuary (Goss-Custard et al., 2006).

No case of kleptoparasitism or territorialism was observed among the foraging Black-winged

Stilts at any of the foraging sites possibly because there were enough prey items during the

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study period. There was also no observed occurrence of kleptoparasitism between Black- winged Stilts and other species probably because of differences in preferred prey and the modes of resource utilization (Choi et al., 2017).

Black-winged Stilts foraged at various water depths, juveniles were however, observed foraging at the shallower edges. This is likely due to limitations in body size (length of leg)

(Ntiamoa-Baidu et al., 1998; Nol et al., 2014) and experience. Prey choice and foraging style are also factors determining the depth of water at which individuals foraged (Ntiamoa-Baidu et al., 1998). Juveniles may prefer aquatic insects which are abundant at the shallow edges while adults may forage on fishes which can be found mostly within the water column.

Fingerlings were abundant at the shallow edges of the water and the juveniles may be exploiting these. On one occasion, Black-winged Stilts foraged in belly-deep water. This has previously been reported by Goriup (1982).

5.2.3. Black-winged Stilt Foraging style

Foraging style influences foraging success and is a response to type of prey, prey abundance and other environmental factors such as water depth and turbidity. Goriup (1982) explains that

Black-winged Stilts used the plunging feeding style opportunistically when there is clear water and abundant prey. During this study, plunging was observed when the water level was high enough for the head to be immersed. Pecking and probing were also observed but not as frequently as plunging. The few occasions when a Black-winged Stilt was observed foraging on land, the feeding style used was pecking. In shallow water, probing, pecking and scything were observed but no plunging, basically because the water level was too low to allow plunging.

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Contrary to reports by Goriup (1982), pecking was not the most frequently used feeding style; the most frequently used feeding style used by the Black-winged Stilt was plunging (39%) followed by probing (29%) and then pecking (20%). This could be due to the foraging sites and conditions during this study. For instance as Goriup (1982) mentions, the foraging sites where Black-winged Stilts plunged more had a lot of water and were occasionally flooded.

There was fishing activity going on nearby at the foraging sites within the wetland indicating that there was abundant fish in the water which was also clear so it makes sense that plunging was the most frequently used feeding style. As previously recorded by Hamilton (1975) for the

Avocet and Black-necked stilt, Black-winged Stilts were not observed drinking. Goriup (1982) also did not observe drinking and postulated that Black-winged Stilts may be obtaining sufficient moisture from food, thus there is no need for drinking. Pecking, filtering and scything rates did not differ between the sites. Probing rate however differed between FORS1 in the wetland and the ESFT.

Foraging success (intake rate) was 41% and varied between foraging site 1 and the estuary foraging site. The lowest intake rate was recorded at the estuary foraging site. The intake rates computed were based on observed head bobbing movement that signaled swallowing after a foraging attempt and thus may be an underestimation since not all intakes elicited the head bobbing motion. Also Black-winged Stilts were sometimes observed foraging for a while without the swallowing motion. It is assumed that if there were no prey items there, the Black- winged Stilts would not forage there especially when there were other foraging sites to choose from (Goss-Custard et al., 2006). Dias et al. (2008) mention that for waders feeding on benthic invertebrates; the maximum intake rate is constrained by searching and handling time. This is probably why intake rate was lowest at the estuary. At foraging sites 1 and 2 however, there were other prey items to forage on. Dias et al., (2008) also indicate that “at high densities

(above 100), waders may significantly decrease their intake rate”.

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CHAPTER SIX: CONCLUSIONS AND RECOMMENDATIONS

6.1. Conclusions

The following conclusions were drawn from the study:

 Presence of water is a factor that determines both the onset of egg laying and nest site

selection. Almost all nests were near water where aquatic organisms could be

obtained readily for food. The exact location of nests is influenced by safety from

predators and floods.

 Presence of vegetation does not influence selection of breeding site. More than half of

all nests encountered were on bare ground. Camouflage and safety of the nest are

important factors when it comes to Black-winged Stilts nest material selection.

 Egg size (length, width) and weight have a positive relationship with order of laying.

The first egg laid is bigger and heavier than subsequent eggs laid in the same nest.

 Distance of a nest to road was the most important factor that influenced nest success.

This is a measure of safety as the closer the nest is to the road, the easier it is to be

predated on by domestic dogs.

 Activity rhythm of Black-winged Stilts showed daily, monthly, seasonal and yearly

variations. There were variations in daily and monthly patterns determined by weather

conditions and tidal cycle. Activity rhythm also differed between breeding and non-

breeding seasons.

 Black-winged Stilts spend on average 51% of the diurnal time foraging.

 Presence of water influenced nest site selection as well as foraging areas of Black-

winged Stilts. They would abandon areas where the water has dried during the dry

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season to more inundated areas. They were thus found mostly in the old salt pans and

mud flats that were adjacent riverine systems.

 The depth of water influences the foraging style adopted by Black-winged Stilts. For

example pecking was used when the water was shallower while plunging was used

when the water was deeper.

6.2. Recommendations

Based on the findings of this study, the following are recommendations:

 Studies of the breeding and foraging ecology of the Black-winged Stilt should be

continued to understand further the factors that delimit the nesting and feeding

behavior of the Black-winged Stilt in Ghana. The study has revealed that there is

yearly variation. A long-term study will help to understand how yearly fluctuations in

climate patterns, as well as other environmental parameters affect the breeding

behavior of Black-winged Stilts.

 Other aspects of the ecology of the Black-winged Stilt should be investigated to also

determine and understand which other factors influence the survival. A thorough

study into the dynamics of disturbance is recommended. This would give an accurate

measure of how interference affects breeding success and foraging success of the

species. Also, long-term data on the time-activity budget and foraging ecology should

be collected throughout the year to provide an in-depth measure of seasonal and

temporal variations in activity rhythm and foraging behavior as well as intensity.

 Water levels during the rainy season when Black-winged Stilts breed should be

regulated by the Ghana Water Company Limited (GWCL) operating the Weija Dam

to prevent flooding levels that wash away nests and eggs of the Black-winged Stilt as

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flooding has been shown to be one of the most important causes of nest failure and

egg loss.

 Another important cause of nest failure and egg loss was predation by stray dogs, it is

therefore recommended that management of the salt pans should take measures to

limit access of the sites to the stray dogs.

 Rainfall appeared to influence the onset of egg laying. The impact of changing

climate should be investigated to provide insight into the dynamics of rainfall

patterns, flooding, prey availability and abundance and how these affect foraging

waders in Ghana.

 Finally, it is recommended that the study should be expanded to include other waders

at the site, especially those that also breed there to understand the intricate

relationships that exist between them and how they adapt to changes in the

environment as well as how they deal with environmental stressors.

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Piersma, T. (1994). Close to the edge : energetic bottlenecks and the evolution of migratory pathways in knots. Retrieved from http://agris.fao.org/agris- search/search.do?recordID=AV20120156986 Piersma, Theunis, & Ntiamoa-Baidu, Y. (1995). Waterbird ecology and the management of coastal wetlands in Ghana. Potts, G. R., Coulson, J. C., & Deans, I. R. (1980). Population Dynamics and Breeding Success of the Shag , Phalacrocorax aristotelis , on the Farne Islands , Northumberland. British Ecological Society, 49(2), 465–484. Quintana, F., & Yorio, P. (2018). Competition for Nest Sites between Kelp Gulls ( Larus dominicanus ) and Terns ( Sterna maxima and S . eurygnatha ) in Patagonia. The Auk. 115(4), 1068–1071. Rais, M., Kabeer, B., Anwar, M., & Mehmood, T. (2010). Effect of habitat degradation on breeding water birds at Kallar Kahar lake district Chakwal. The Journal of Animal & Plant Sciences. 20(4), 318–320. Ramsar Convention, B. (1998). Wetland Values and Functions. Ramsar Bureau, Switzerland. Ramsar Information Sheet. (2015). Ramsar Information Sheet Ghana Densu Delta Ramsar Site Color codes. (564), 1–25. Reneerkens, J., Benhoussa, A., Boland, H., Collier, M., Grond, K., Günther, K., … Hansen, J. (2009). Sanderlings using African – Eurasian flyways : a review of current knowledge. Wader Study Group Bull., 116(1), 2–20. Robert, M., & Mcneil, R. (1989). Comparative day and night feeding strategies of shorebird species in a tropical environment. Ibis, 131(1), 69–79. https://doi.org/10.1111/j.1474- 919X.1989.tb02745.x Rolet, C., Spilmont, N., Davoult, D., Goberville, E., & Luczak, C. (2015). Anthropogenic impact on macrobenthic communities and consequences for shorebirds in Northern France : A complex response. Biological Conservation, 184, 396–404. https://doi.org/10.1016/j.biocon.2015.02.016 Rose, P. M., & Scott, D. A. (1997). Waterfowl Population Estimates (Second Edi). Wetlands International Publ. 44, Wageningen, The Netherlands. Sandercock, B. K. (1996). Egg-Capping and Eggshell Removal by Western and Semipalmated Sandpipers. American Ornithological Society, 98(2), 431–433. Schnell, G. D., Woods, B. L., & Ploger, B. J. (1983). Brown Pelican foraging success and kleptoparasitism by Laughing Gulls. American Ornithological Society, 100(3), 636–644. Skutch, A. F. (1976). Parent birds and their young. University of Texas Press. Austin. Smit, J., & Piersma, T. (1994). Number, midwinter distribution and migration of wader populations using the East Atlantic flyway. Bulletin Mensuel de l’Office National de La Chasse (France). Retrieved from http://agris.fao.org/agris- search/search.do?recordID=FR9702874 Smith, J. N. M., & Sweatman, H. P. A. (1974). Food-Searching Behavior of Titmice in

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Patchy Environments. Ecology, 55(6), 1216–1232. https://doi.org/10.2307/1935451 Snow, D. W., & Perrins, C. M. (1998). The Birds of the Western Palearctic (Concise Edition): Volume 1 Non-Passerines by D.W. Snow & C.M. Perrins: Oxford University Press, Oxford - Berwyn Books. Retrieved from https://www.abebooks.co.uk/servlet/BookDetailsPL?bi=16459011351&searchurl=tn%3 Dconcise%2Bbirds%2Bof%2Bthe%2Bwestern%2Bpalearctic%26sortby%3D20%26an %3Dsnow%2Band%2Bperrins&cm_sp=snippet-_-srp1-_-title5 Sordahl, T. A. (1994). Eggshell Removal Behavior of American Avocets and Black-Necked Stilts. Journal of Field Ornithology, 65(4), 461–465. Tasker, C. R., & Mills, A. J. (1981). A Functional Analysis of Courtship Feeding in the Red- Billed Gull , Larus Novaehollandiae Scopulinus. Behaviour, 77(4), 222–241. Retrieved from http://www.jstor.org/stable/4534121 The Ramsar Convention Secretariate. (2018). The Ramsar Convention and its mission | Ramsar. Retrieved July 8, 2018, from https://www.ramsar.org/about/the-ramsar- convention-and-its-mission Tinarelli, R. (1991). Habitat preference and breeding performance of the Black-winged Stilt (Himantopus himantopus) in Italy. Wader Study Group Bulletin. 65:58-62. Tinbergen, N., Broekhuysen, G. J., Feekes, F., Houghton, J. C. W., Kruuk, H., & Szulc, E. (1962). Egg Shell Removal by the Black-Headed Gull , Larus ridibundus L .; A Behaviour Component of Camouflage. Brill, 19(1), 74–117. Retrieved from http://www.jstor.org/stable/4533006 Tomiyama, T., Komizunai, N., Shirase, T., Ito, K., & Omori, M. (2008). Spatial intertidal distribution of bivalves and polychaetes in relation to environmental conditions in the Natori River estuary , Japan. Estuarine, Coastal and Shelf Science, 80(2), 243–250. https://doi.org/10.1016/j.ecss.2008.08.003 Toral, G. M., & Figuerola, J. (2012). Nest Success of Black-Winged Stilt Himantopus himantopus and Kentish Plover Charadrius alexandrinus in Rice Fields, Southwest Spain. Ardea, 100(1), 29–36. https://doi.org/10.5253/078.100.0106 Ueng, Y. T., Wang, J. P., Hou, lucy P. C., & Perng, J. J. (2009). Diet of Black-winged Stilt Chicks in Coastal Wetlands of Southwestern Taiwan. The International Journal of Waterbird Biology , Vol . 32 , No . 4 Pu. 32(4), 514–522. van Eerden, M. R. (1984). Waterfowl movements in relation to food stocks. Wagner, M. (2004). Managing Riparian Habitats For Wildlife. Texas Parks and Wildlife. Westmoreland, D. (2008). Evidence of Selection for Egg Crypsis in Conspicuous Nests. Wiley, 79(3), 263–268. Westmoreland, D., & Best, L. B. (1986). Incubation Continuity and the Advantage of Cryptic Egg Coloration to Mourning Doves. Wilson Ornithological Society, 98(2), 297–300. Willoughby, N., Grimble, R., Ellenbroek, W., Danso, E., & Amatekpor, J. (2001). The wise use of wetlands : identifying development options for Ghana ’ s coastal Ramsar sites. Hydrobiologia. 458: 221–222.

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World Wildlife Fund Canada. (2015). The value of wetlands | WWF. WWF Global, (February), 2–3. Retrieved from http://wwf.panda.org/about_ur_earth/about_freshwater/intro/value/ Yeates, G. K. (1938). Some breeding-habits of the black-winged stilt. British Birds. 35(42): 42–46.

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Appendices

Appendix 1

Modelling nest success of the Black-winged Stilt.

Model P-value AIC

Nestsuc~Year 0.08979 383.82

Nestsuc~Site 0.5001 387.31

Nestsuc~1sight 1.931e-06 364.04

Nestsuc~Clutch size 1.864e-09 350.59

Nestsuc~Nest location 2.931e-06 364.84

Nestsuc~veg 0.2285 385.25

Nestsuc~wip 0.8437 386.66

Nestsuc~dtr 0.0033 378.08

Nestsuc~Dtcn 0.0246 381.65

Nestsuc~mpd 0.656 386.5

Nestsuc~Egg length 0.1526 384.65

Nestsuc~Egg width 0.2309 385.26

Nestsuc~Egg weight 0.6331 386.47

Nestsuc=nest success (successful/unsuccessful), 1sight=number of egg at first sighting, Veg = presence or absence of vegetation, wip = presence of water in pan or around the nest, dtr = distance to road, dtcn = distance to closest nest, mpd = minimum permissible distance.

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Appendix 2

Stepwise backward model selection with AIC as selection criterion

Model AIC

nestsuc ~ year + site + totegg + nest.location + veg + wip + dtr + dtcn + m 328.16

pd + egg.length + egg.width + egg.weight

nestsuc ~ year + site + totegg + nest.location + veg + wip + dtr + dtcn + m 326.26

pd + egg.length + egg.weight

nestsuc ~ year + site + totegg + nest.location + veg + wip + dtr + dtcn + m 324.63

pd + egg.length

nestsuc ~ year + site + totegg + nest.location + wip + dtr + dtcn + mpd + e 323.05

gg.length

nestsuc ~ year + site + totegg + nest.location + wip + dtr + dtcn + egg.lengt 321.5

nestsuc ~ year + site + totegg + nest.location + wip + dtr + dtcn 320.05

nestsuc ~ year + totegg + nest.location + wip + dtr + dtcn 318.87

nestsuc ~ year + totegg + nest.location + dtr + dtcn 317.15

Nestsuc=nest success (successful/unsuccessful), 1sight=number of egg at first sighting, totegg=clutch size, veg = presence or absence of vegetation, wip = presence of water in pan or around the nest, dtr = distance to road, dtcn = distance to closest nest, mpd = minimum permissible distance.

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Appendix 3

Modelling egg hatchability (number of eggs hatched per nest)

Model p-value R2 AIC

egghatch ~ year 0.4597 0.001989 1099.653

egghatch ~ site 0.4346 0.006064 1100.52

egghatch ~ totegg 2.2e-6 0.2582 1017.478

egghatch ~ nest.location 0.00106 0.0383 1089.386

egghatch ~ veg 0.0278 0.01744 1095.332

egghatch ~ wip 0.725 0.00045 1100.08

egghatch ~ dtr 0.009608 0.02413 1093.437

egghatch ~ dtcn 0.073 0.01164 1096.961

egghatch ~ mpd 0.452 0.002059 1099.634

egghatch ~ egg.length 0.09311 0.01022 1097.359

egghatch ~ egg.width 0.3171 0.003639 1099.195

egghatch ~ egg.weight 0.8515 0.0001276 1100.169

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Appendix 4

Stepwise backward model selection using AIC

Model AIC

egghatch ~ year + site + totegg + nest.location + veg + wip + dtr + dtc 217.44

n + mpd + egg.length + egg.width + egg.weight

egghatch ~ year + totegg + nest.location + veg + wip + dtr + dtcn + m 214.58

pd + egg.length + egg.width + egg.weight

egghatch ~ year + totegg + nest.location + veg + wip + dtr + dtcn + eg 212.62

g.length + egg.width + egg.weight

egghatch ~ year + totegg + nest.location + veg + wip + dtr + dtcn + eg 210.71

g.length + egg.width

egghatch ~ year + totegg + nest.location + veg + dtr + dtcn + egg.lengt 208.9

h + egg.width

egghatch ~ year + totegg + nest.location + dtr + dtcn + egg.length + eg 207.64

g.width

egghatch ~ year + totegg + nest.location + dtr + dtcn + egg.length 207.24

egghatch ~ year + totegg + nest.location + dtr + dtcn 206.6

Egghatch= number of eggs hatched, totegg=number of eggs in nest, dtr=distance to road, dtcn=distance to closest nest, veg=presence or absence of vegetation, wip=water in pan (presence or absence of water near nest).

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Appendix 5

Densities of macroinvertebrates at the estuary

Sampling Replicate Sediment Macroinvertebrate Density station level m-2

1 1 Top 5cm Polychaete 1796

1 Bottom 10 cm

2 Top 5cm Hastula 138

2 Bottom 10 cm

3 Top 5cm Polychaete 276

3 Bottom 10 cm

2 1 Top 5cm Polychaete 276

1 Bottom 10 cm

2 Top 5cm Polychaete 829

2 Bottom Polychaete 967 10 cm

3 Top 5cm

3 Bottom 10 cm

3 1 Top 5cm Polychaete 1382

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1 Bottom Polychaete 138 10 cm

2 Top 5cm Polychaete 967

2 Bottom 10 cm

3 Top 5cm Polychaete 691

3 Bottom Polychaete 138 10 cm

4 1 Top 5cm Polychaete 1938

1 Bottom Polychaete 138 10 cm

2 Top 5cm Polychaete 414

2 Bottom 10 cm

3 Top 5cm Polychaete 138

3 Bottom 10 cm

**The data shown in this table is from samples collected at the ESTF (estuary foraging site)

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