Analysis of Long-Term Productivity Monitoring and Foraging Area Identification of Breeding Common Terns in Coastal New Hampshire

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Master's Theses and Capstones Student Scholarship

Winter 2018

ANALYSIS OF LONG-TERM PRODUCTIVITY MONITORING AND FORAGING AREA IDENTIFICATION OF BREEDING COMMON TERNS IN COASTAL NEW HAMPSHIRE

Jessica Marie Carloni University of New Hampshire, Durham

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JESSICA MARIE CARLONI

B.T., State University of New York at Cobleskill, 2005

THESIS

Submitted to the University of New Hampshire in Partial Fulfillment of the Requirements for the Degree of

Master of Science in Natural Resources: Wildlife and Conservation Biology

December 2018 This thesis has been examined and approved in partial fulfillment of the requirements for the degree of Master’s in Wildlife and Conservation Biology by:

Thesis Director, Dr. Peter J. Pekins Professor Wildlife Ecology, University of New Hampshire

Dr. Erik Chapman Director, New Hampshire Sea Grant

John Kanter Senior Wildlife Biologist, National Wildlife Federation

December 14, 2018 Date

Original approval signatures are on file with the University of New Hampshire Graduate School.

ACKNOWLEDGEMENTS

I am forever grateful to John Kanter for providing me the opportunity to work on this project; without his support and belief in me, none of this would have been possible. I’d also like to extend my gratitude to Dr. Erik Chapman and Dr. Peter Pekins for their guidance and advice throughout this process. Thank you to all the dedicated field staff who worked on Seavey

Island over the years, especially Nora Papian, Virginia Winkler, Johanna Pedersen, and Juliana

Hanle. I am also grateful to Dan and Melissa Hayward for managing the tern project on Seavey

Island for so many years and providing valuable input about my field research.

I am extremely grateful to Katie Callahan for providing assistance with ArcGIS and analyzing the movement data. I would also like to thank Dr. Elizabeth Craig for her advice with

Chapter 1; her knowledge of terns was extremely beneficial. I’m also extremely grateful to Ed and Julie Robinson for being such positive mentors for me as a young aspiring wildlife biologist; their passion was contagious! Thanks to Patrick Tate who kept reminding me to jump through the hoops; I can’t believe there are no more!

I’m especially thankful to my family for their support. To my sister Jenn, thank you for the constant guidance throughout and providing the tough love when I needed it. I would like to thank my Mom for her continued encouragement and genuine interest in my work. I’m also grateful to my Dad for always making me laugh. Finally, I would like to thank my husband,

Josh for his unrelenting support, motivation, advice, and assistance in the field; you are truly amazing!

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Funding for this research was provided by Nongame and Endangered Wildlife Program, State and Tribal Wildlife Grants Program, NH Moose plate dollars and private donations through NH

Fish and Game.

TABLE OF CONTENTS ACKNOWLEDGEMENTS ...... ii LIST OF TABLES ...... iii LIST OF FIGURES ...... iv ABSTRACT ...... vi INTRODUCTION ...... 1 STUDY AREA ...... 8 CHAPTER 1: ANALYSIS OF LONG-TERM MONITORING OF PRODUCTIVITY OF A COMMON TERN RESTORATION COLONY IN NEW HAMPSHIRE ...... 10 Introduction ...... 10 Methods ...... 18 Results ...... 23 Discussion ...... 32 CHAPTER 2: FORAGING AREAS OF BREEDING COMMON TERNS ON SEAVEY ISLAND NEW HAMPSHIRE AND GPS DATA LOGGER ATTACHMENT METHOD ...... 41 Introduction ...... 41 Methods ...... 43 Results ...... 46 Discussion ...... 53 LIST OF REFERENCES ...... 60 APPENDICES ...... 78 APPENDIX A ...... 79 APPENDIX B ...... 80

LIST OF TABLES

TABLE PAGE

1-1 Total number of nests within the 14 monitored productivity plots by year on Seavey Island, NH 20

1-2 Single linear regression coefficients of environmental variables and common tern productivity during the laying, chick rearing and entire nesting periods on Seavey Island NH. 27

1-3 Linear regression coefficients between prey species and reproductive success on Seavey Island NH. 28

1-4 Pearson correlation coefficients between the initial lay date (ILD) of common terns and environmental variables during the laying period. 30

1-5 Pearson correlation coefficients between duration of laying (DOL) of common terns and environmental variables during the laying period. 31

2-1 Tagging information for individual common terns fitted with GPS data loggers in 2015 on Seavey Island, NH. 48

2-2 Sample sizes and foraging trip characteristics of breeding common terns with GPS data loggers on Seavey Island, NH in 2015. 50

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LIST OF FIGURES

FIGURE PAGE

1 The breeding and wintering distribution of common terns in North America (Nisbet 2002). 2

2 Actively managed islands of breeding seabird colonies in the Gulf of Maine (USFWS). 5

3 Location of common tern breeding colony on Seavey and White Islands, New Hampshire. 9

4 Major currents of the Gulf of Maine. http://www.gulfofmaine- census.org/about-the-gulf/oceanography/circulation/ 9

1-1 Annual number of nesting pairs and level of stability (---) of common terns on Seavey Island 1999-2015. 23

1-2 Annual productivity (sum of chicks fledged/sum of nests) and recent level of stability (---) of common terns monitored for productivity on Seavey Island 1999-2015. 24

1-3 Annual colony production and level of stability (---) of common terns on Seavey Island 1999-2015. 25

1-4 Annual nest density (sum nests in plots/sum of plots) and productivity of common terns on Seavey Island 1999-2015. 26

1-5 Annual proportions of five most delivered prey by year to common tern chicks during the feeding study on Seavey Island 1999-2015. 28

1-6 Initial lay date of common terns from nests monitored for productivity on Seavey Island 1999-2015 29

1-7 Final lay date of common terns from nests monitored for productivity on Seavey Island 1999-2015 30

1-8 Duration of laying period (DOL) (with trend line) of common terns from nests monitored for productivity on Seavey Island 1999-2015. 31

2-1 Common tern with GPS data logger attached with glue and Tesa tape before release (left) and with GPS logger removed (right) in 2014 on Seavey Island, NH. 47

2-2 Common tern with GPS data logger sutured on back before release (left) and common tern sitting on nest with GPS data logger sutured on back (right) in 2015 on Seavey Island, NH 47

2-3 All GPS locations (n = 1,202) collected from 19 common terns with GPS data loggers in 2015 on Seavey Island, NH. 51

2-4 The 3 primary foraging areas (n = 21 trips by 12 birds) of common terns with GPS data loggers in 2015 on Seavey Island, NH. 51

2-5 Other foraging locations (n= 4 trips by 4 birds) of common terns with GPS data loggers in 2015 on Seavey Island, NH. 52

ABSTRACT

ANALYSIS OF LONG-TERM PRODUCTIVITY MONITORING AND FORAGING AREA

IDENTIFICATION OF BREEDING COMMON TERNS IN COASTAL NEW HAMPSHIRE

Jessica Marie Carloni

University of New Hampshire, December, 2018

To restore New Hampshire tern populations, the Isles of Shoals Seabird Restoration

Project was initiated in 1997 by New Hampshire Audubon and the New Hampshire Fish and

Game Department, and is currently administered through a partnership between Shoals Marine

Laboratory and New Hampshire Fish Game Department. This initial program was effective and substantial numbers of common terns and lower numbers of roseate and arctic terns have returned to nest on White and Seavey Islands. Analysis of long-term productivity monitoring over 17 years indicates recent stability in the colony with approximately 2,800 nesting pairs with an average productivity rate of 1.11 chicks fledged per nest in recent years. The colony has produced approximately 38,000 chicks during the 17-year monitoring period. It’s likely that the carrying capacity of Seavey Island has been reached, possibly caused by reduced prey availability; recent annual variability may reflect expected dynamics in carrying capacity. In addition, common terns are laying earlier and extending the laying season longer, possibly in response to a warming Gulf of Maine.

GPS data loggers were attached to breeding common terns at Seavey Island to identify important foraging areas. The glue and Tesa tape method of attachment of GPS data loggers was determined inappropriate for use on common terns. The suture attachment method proved effective and reproductive success of tagged terns was not influenced negatively in comparison to a control group. Data loggers attached to 19 terns in 2015, yielded 428.8 h of activity in which 50 foraging trips occurred. Foraging occurred primarily at three locations associated with fronts that aggregate zooplankton and larval fish: the mouths of the Piscataqua and Merrimack

Rivers (63%) and an offshore area approximately 20 km East of Seavey Island (28%). Other foraging locations (11%) included an area between the Isles of Shoals and the NH shoreline, the mouth of Hampton Harbor, and ~ 3 km east and 4 km northwest of the Isles of Shoals. The total combined distance traveled was 1,383 km (range = 19 to 174 km) of which 879 km (64%) were presumed foraging trips. The mean trip length was 28 ± 11 km and the mean maximum distance from the colony was 16 ± 5 km. The maximum foraging distance was 24 km and the mean trip duration 102 ± 28 min. GPS data logger technology provided important, previously unknown locations, where common terns forage in coastal NH.

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INTRODUCTION

Common terns (Sterna hirundo) are the most widespread tern in the northeastern United

States. In North America, their breeding range extends along the Atlantic coast from the

Canadian Maritimes to South Carolina and the Gulf coast of Louisiana (Fig. 1). Breeding pairs are also found inland throughout much of Canada and the Great Lakes region (Nisbet 2002).

The estimated number of nesting pairs in North America is approximately 150,000 with the majority (90,000) along the Atlantic Coast (Nisbet 2012). The entire global population of common terns is 1,600,000–4,600,000 individuals (Birdlife International 2015). Common terns are listed as a State Threatened species, and a species of greatest conservation need in the State of New Hampshire, which is located in the central part of the Northwest Atlantic breeding range.

Seavey Island, in NH, is part of the Isles of Shoals and supports 99% of the total breeding population in the state (De Luca 2006) and is one of many managed tern colonies in the Gulf of

Maine (GOM) (Fig. 2).

Seavey Island also maintains lesser numbers of breeding roseate (Sterna dougallii) and arctic terns (Sterna paradisaea). Roseate terns are both state and federally listed as endangered

(De Luca 2006, Pyzikiewicz 2006), with 90% of the northeast population nesting on three islands: Great Gull Island, New York (NY), Bird Island, Massachusetts (MA), and Ram Island,

MA (Nisbet 2014). The management of common tern colonies is critical to the survival of the federally endangered roseate tern (De Luca 2006) in the northeast, as they tend to breed within common tern colonies (USFWS 1998, Nisbet 2014).

The breeding range of arctic terns in North America stretches from the Canadian Arctic south along the eastern coastline to Massachusetts, and they also nest in high arctic areas of

Europe and Asia. Significant breeding areas in North America include Newfoundland, the Gulf of St. Lawrence, Nova Scotia, and the GOM (Kress and Hall 2004). In 2014, 88% (2,209 pairs) of arctic terns in the GOM nested on four islands in Maine: Petit Manan, Seal Island, Matinicus

Rock, and Metinic (GOMSWG Minutes 2014). Over the past 10 years, Seavey Island has averaged only 4 pairs of artic terns (GOMSWG Minutes 2015), likely because it is located at the southern extent of the breeding range.

Figure 1. The breeding and wintering distribution of common terns in North America (Nisbet 2002).

In the 1800s, terns were close to extirpation in the GOM due to their high exploitation in the millinery trade. Subsequent restoration efforts have been measurable, with >20,000 common tern pairs nesting at 47 sites by the early 2000s (Kress and Hall 2004). Although viewed as a conservation success story, their population is still below historical levels and continuous management is required to maintain populations (Nisbet 2002, Kress and Hall 2004). For example, the North American common tern population has declined 70% overall in the last 40 years (Butcher and Niven 2007). In the Northeast, the majority of the population (84%) nests on eight islands making them susceptible to catastrophic events such as oil spills, predation, or severe weather events (Kress and Hall 2004, De Luca 2006).

The Isles of Shoals historically supported considerable numbers of terns (DeLuca 2006) with the largest colony on Lunging Island that had approximately 1,500 to 2,000 pairs of common, 50-60 pairs of roseate, and 25-30 pairs of Arctic terns (Jackson 1947). Duck and

Lunging Islands supported high numbers of breeding terns in the mid-1800 and 1900s (Jackson

1947, Borror and Holmes 1990), but Lunging Island was abandoned in the mid 1940-50s because of displacement by herring gulls (Larus argentatus) (Drury 1973, Erwin 1979). The near extirpation of terns from the feather trade provided gulls with more nesting habitat that, in turn, lead to the increase of herring and great black-backed gulls (Larus marinus) (Brown and

Nettleship 1984, Buckley and Buckley 1984) that prey on tern eggs and young (Nisbet 2002).

The presence of open landfills and lobster/fishery waste also contributed to a growing gull population in seacoast NH (Goodale 2000) and other coastal areas (Kadlec and Drury 1968,

Drury 1973, Nisbet 1978, Oro et al. 1995, Chapdelaine and Rail 1997). The displacement by gulls forced terns to occupy less suitable nesting locations near the mainland making them more susceptible to predators such as gulls, coyote (Canis latrans), mink (Neovison vison) (De Luca

2006), muskrat (Ondatra zibethicus), rats (Rattus sp.) (Buckley and Buckley 1984), great horned owls (Bubo virginianus), black-crowned night herons (Nycticorax nycticorax) (Hunter and

Morris 1976), and peregrine falcons (Falco peregrinus) (Nisbet 1992). Smaller colonies of terns were reported in Seabrook Beach, Hampton Marsh, Back Channel Islands in Newcastle, and in

Little and Great Bay Estuaries (White 1928, Smith 1982, Kress and Hall 2004).

To restore New Hampshire tern populations, the Isles of Shoals Seabird Restoration

Project was initiated in 1997 by New Hampshire Audubon (NHA) and the New Hampshire Fish and Game Department (NHFG), and is currently administered through a partnership with the

UNH Shoals Marine Laboratory, led by NHFG. Over the years, this project successfully employed strategies to both attract terns and deter gulls on White and Seavey Islands. In 1997, tern decoys were placed on the island and tern colony sounds were played from loud speakers in an attempt to attract terns, a successful approach at other locations (Kress 1983). This initial program was effective, and with continued effort to reduce gulls since 1997, substantial numbers of common terns and lower numbers of roseate and arctic terns have returned to nest on White and Seavey Islands (De Luca 2006). The island is posted as an endangered species breeding site with public use prohibited from 1 May through 1 September (De Luca 2006), as are many other seabird breeding islands in the GOM (Fig. 2).

Figure 2. Actively managed islands of breeding seabird colonies in the Gulf of Maine (USFWS).

Research priorities for common terns highlighted in the NHFG Wildlife Action Plan

(2006) include:

1) assess and monitor the effects of aquaculture, fishing practices, and other stressors

on terns, tern predators, and habitats,

2) identify and protect, if feasible, critical habitats such as foraging, staging, and

wintering areas, and

3) identify seasonal and spatial variation in prey (composition and abundance) and

potential effects on colony productivity (De Luca 2006).

Common terns comprise the majority of the three tern species found in the GOM and management of common tern colonies is vital to the survival of the federally endangered roseate

5 tern in the Northeast (De Luca 2006, Kress and Hall 2004), yet fundamental information needed to effectively manage terns is lacking. It is critical to continue intensive management of common tern colonies to prevent decline in population and productivity from predation and loss of suitable habitat (Kress and Hall 2004). A considerable investment is required to maintain management of these colonies, and appropriate funding and staffing are major limiting factors in the region (Kress and Hall 2004). Other limiting factors include access to suitable nesting and foraging habitat, predation, weather, food availability and quality, competition, human disturbance, commercial fisheries, erosion, and climate change (Kress and Hall 2004).

Recently, the Northeast Fisheries Science Center (NEFSC 2013) suggested that primary productivity patterns in the GOM have shifted in both magnitude and phenology, and that temperature is increasing at a much faster rate than in the rest of the Northwest Atlantic (Mills et al. 2013). Both of these changes could pose major threats to the maintenance and growth of tern populations in the region.

In order to maintain the common tern colony restored at Seavey Island, it is important to not only continue efforts to limit predation, but to also monitor and study factors that influence reproductive successes and bioenergetics. In particular, it is important to identify where the birds feed during the breeding season, and to distinguish the composition and trends of available prey species (DeLuca 2006). Observations of terns indicate that they forage in Great Bay, Hampton

Harbor, and the Piscataqua River; yet, exact locations and habitat characteristics at these sites are unknown. Further, little is known about critical foraging, staging, and wintering areas that would help establish a more complete understanding of vulnerabilities and conservation opportunities in the GOM (DeLuca 2006). Overall, the at-sea foraging ecology of seabirds is largely unstudied

(Hall et al. 2000, Granadeiro et al. 2002, Shealer 2002) due to the complexities of conducting research at sea (Black 2002).

Research presented here was designed to provide insight into the foraging areas of common terns nesting on Seavey Island and factors that influence common tern productivity from a time-series of colony-specific data from 1999-2015. Chapter 1 provides an analysis of the productivity data amassed from 17 years of intensive monitoring, and environmental variables were compiled to explore potential effects on reproductive success. Chapter 2 identifies important foraging areas of common terns nesting at the Isles of Shoals through the use of GPS data loggers, the effects on productivity of short-term attachment of the data loggers, and description of a successful attachment method for these plunge-diving seabirds.

STUDY AREA

The study was conducted on Seavey Island, NH (42°58’N, 70°37’W) (Fig. 3), which with

9 other islands, form the Isles of Shoals located approximately 9 km off the coast of Rye Beach,

NH. The island is approximately 1.5 ha and composed mainly of granite boulders with pockets of vegetation forming a tombolo cluster with neighboring White Island at low tide. The predominant vegetation is grasses, yarrow (Achillea millefolium), seaside goldenrod (Solidago sempervirens), black mustard (Brassica nigra), and dodder (Cuscuta gronovii) (De Luca et al.

2006).

Seavey Island supports approximately 2,880 nesting pairs of common terns, 74 pairs of roseate terns, and 3 pairs of arctic terns (Terns LLC 2015) and is located within the GOM, one of the most biologically productive ecosystems in the world supporting over 3,000 species

(Sherman and Skjoldal 2002, Parker 2009, Thompson 2010). More than 184 seabird species identified in the GOM benefit from its rich abundance of food (Thompson 2010). The nutrient rich waters are fed by the cold, deep Labrador Current which enters south of Nova Scotia along the Northeast Channel (Fig. 4) (Schlitz and Cohen 1984, Ramp et al. 1985, Brooks and

Townsend 1989, Townsend 1991, 1998).

Figure 3. Location of common tern breeding colony on Seavey and White Islands, New Hampshire.

Figure 4. Major currents of the Gulf of Maine. http://www.gulfofmaine-census.org/about-the- gulf/oceanography/circulation/

CHAPTER 1

ANALYSIS OF LONG-TERM PRODUCTIVITY MONITORING OF A COMMON TERN RESTORATION COLONY IN NEW HAMPSHIRE

Introduction

Productivity

Numerous factors can influence reproductive success of common terns. The most important in NH include displacement by gulls, predation, suitable nesting habitat, prey availability/quality, competition, climate change and weather, and commercial fisheries impacts

(Buckley and Buckley 1984, Nisbet 2002, Kress and Hall 2004, De Luca 2006). Managed colonies tend to have limiting factors associated with competition for nesting sites, mates, and food resources. Predators can reduce success even at the best managed colonies, as predation is difficult to fully control (Kress and Hall 2004). Deluca (2006) noted that productivity of the

Seavey Island colony in 2004 was less than 1.1 – 1.8 chicks per nest, the threshold level to sustain population growth (DiCostanzo 1980), and stressed the importance of monitoring and evaluating declines in productivity.

Suitable Nesting Sites

The availability of suitable nesting islands is crucial to the distribution of island nesting terns (Kress and Hall 2004, Deluca 2006). Optimal islands have few to no predators or gulls, optimal vegetative height and substrate, and accessible and productive foraging areas in close proximity (Kress and Hall 2004). Suitable nesting habitat for common terns is open rock/gravel

substrate with approximately 10-40% vegetative cover (Buckley and Buckley 1982, Burger and

Gochfeld 1988, Ramos and del Nevo 1995, Cook-Haley and Millenbah 2002). They prefer open areas with adjacent patches of vegetation for protection from conspecifics and severe weather

(Severinghaus 1982, Houde 1983, Burger and Gochfeld 1988, Nisbet 2002). However, most available nesting habitat on unmanaged islands in the GOM consists of islands with grassy meadows in the center with a narrow margin of rock-vegetation interface (Conkling 1999). This unmanaged suboptimal habitat restricts tern populations to a small number of managed colonies versus distribution amongst numerous small colonies (Kress et al. 1983, Anderson and Devlin

1999, Kress and Hall 2004).

Seabirds deposit large amounts of guano on nesting islands that generally have minimal outside nutrient sources (Polis and Hurd 1996, McMaster 2005, Wait et al. 2005). This byproduct often increases biomass, height, and cover of vegetation due to increased availability of nitrogen and phosphorus, diminishing habitat quality (Anderson & Polis 1999, Sánchez-

Piñero & Polis 2000, Ellis 2005). In the GOM, vegetative cover and substrate type limit common tern nesting habitat (Houde 1983, Nisbet 2002, Kress and Hall 2004). Therefore, colony managers employ a suite of techniques to combat vegetation including weed barriers, burning, hand removal, herbicides, and saltwater application (Lamb 2015); effectiveness increases when multiple techniques are applied in combination (Schwarzer and Koch 2004,

Burbidge 2008).

Competition

One disadvantage for colonial nesting species is the increased potential for intraspecific aggression (Coulson 2002) which can reduce chick survival and breeding success (Quinn et al.

1994). Both interspecific and intraspecific competition for nest sites have limited the success of common terns at some colonies within the GOM (Nisbet 2002). Nesting territory is determined by the male soon after arrival to the island, and eventually is defended by the pair (Nisbet 2002).

Nest aggregations occur most often around edges of preferred patches of vegetation (Nisbet

2002). Kleptoparisitism (stealing of prey) by common terns could force increased foraging effort, and importantly, leave chicks unattended for longer periods (Nisbet et al. 1978, Quinn et al. 1994, Arnold et al. 2004). It occurs more often between conspecifics in dense colonies and when food is limited (Ludwigs 1998), and kleptoparasitic individuals are more productive than non-kleptoparasitic individuals within a population (Shealer et al. 2005, García et al. 2011,

2013).

Predation

Herring and great black-backed gulls rarely take eggs, but predate pre-fledge chicks by grabbing them from the nest and post-fledge chicks by chasing them until they land in water from exhaustion (Whittam and Leonard 1999). When management began at Seavey Island, human interference was necessary to deter gulls and allow terns to recolonize (DeLuca 2006).

Human presence is still required as the inflated local gull population continues to predate terns and compete for nesting habitat (Terns LLC 2015). Non-lethal harassment techniques (i.e., pyrotechnics, human harassment, nest destruction) are used on Seavey Island as recommended in management plans (Donehower et al. 2007). Limited lethal gull control, considered an effective tool for enhancing productivity, is conducted on Seavey Island when gulls repeatedly visit the colony and attempt to predate eggs and young (Guillemette and Brousseau 2001, Terns LLC

2015).

Other predators of adult common terns, eggs, and chicks include coyote (Canis latrans), mink (Neovison vison) (De Luca 2006), muskrat (Ondatra zibethicus), rats (Rattus spp.)

(Buckley and Buckley 1984), great horned owls (Bubo virginianus), black-crowned night herons

(Nycticorax nycticorax) (Hunter and Morris 1976), and peregrine falcons (Falco peregrinus)

(Nisbet 1992). On Seavey Island, gulls are the primary predators of tern chicks followed by episodic mortality by muskrats, peregrine falcons, and snowy owls (Terns LLC 2015). Islands closer to the mainland are exposed to a higher diversity of predators than offshore islands (Hall

1999).

Weather

Seabirds experience a variety of daily, seasonal, and annual weather patterns that affect their habitat, food, ability to forage, and survival. Weather has direct and indirect effects

(Schreiber 2002) and can influence reproductive success, chick growth, food availability, clutch size, ability of birds to locate food, timing of the breeding season, and adult survival (Dobinson and Richards 1964, Dunn 1973, Coulson and Porter 1985, Springer et al. 1986, Anderson 1989,

Schreiber and Schreiber 1989, 1993, Cruz and Cruz 1990, Duffy 1990, Arnould et al. 1996,

Montevecchi and Myers 1996, 1997, Schreiber 1996, Konyukhov 1997, Finney et al. 1999).

Identifying specific weather effects on breeding seabirds is difficult to distinguish from other influences such as age of adults, experience, and nest location (Schreiber 2002); however, weather has been linked to breeding success. For example, a study with yellow-eyed penguins

(Megadyptes antipodes) found significant correlations between breeding population variables

(number of nests, eggs laid and hatched, and number of chicks fledged) and rainfall, sea surface temperature, and air temperature (Peacock et al. 2000).

Climate Change

Of the seabirds monitored world-wide, 70% are declining and climate change is considered a primary global threat (Paleczny et al. 2015). Audubon lists common terns as threatened in their climate report (National Audubon Society 2015), and between 2004 and 2013, the GOM has warmed faster than 99.9% of the global ocean (Pershing et al. 2015). Certain common tern prey species such as red and silver hake have experienced significant, measurable shifts in their range (Pinsky and Fogarty 2012), which could influence their ability to successfully fledge chicks during the breeding season. Over the last four decades, many fish stocks in the Northwest Atlantic have shifted northward to deeper water to exist in an optimal temperature regime (Nye et al. 2009). Sea levels are predicted to rise at least 8 inches, up to as much as 6.6 feet, by 2100 (Parris et al. 2012) which would further constrain available nesting habitat. As the majority of the NH tern population nests on Seavey Island, they are clearly vulnerable to impacts from climate change (De Luca 2006).

Prey Availability and Commercial Fishing

Reproductive success of seabirds has declined following a reduction or collapse in availability of local prey stocks (Hunt 1972, Safina et. al 1988, Monaghan et al. 1989, 1992,

Newton 1998, Litzow et. al. 2002, Suryan et. al. 2002). Because common terns arrive at their breeding sites with depleted energy reserves (Pearson 1968) after an extensive migration from

South America (Austin 1953; Nisbet et al. 2011), the availability of abundant, energy rich prey proximate to colonies is critical to restore breeding condition and fuel reproductive effort. The ability to locate food close to the colony has a direct influence on their reproductive success

(Courtney and Blokpoel 1980).

Commercial fishing has direct and indirect impacts on seabirds, of which some are positive (Tasker et al. 2000). Pelagic feeding seabirds often benefit by following commercial fishing vessels and feeding on bycatch or bait thrown overboard; though terns do not follow commercial boats, they will consume bycatch (Tasker et al. 2000). New England populations of herring and great black backed gulls likely increased from this behavior (Goodale 2000). A negative effect of commercial fishing is that seabirds end up as by-catch in nets or on hooks of long-lines in ground fisheries. In the Northeast, the most affected bird is the northern fulmar

(Fulmarus glacialis) in the Atlantic cod (Gadus morhua) fishery. Common murres (Uria aalge), black guillemots (Cepphus grylle), razorbills (Alca torda), greater shearwaters (Puffinus gravis), sooty shearwaters (P. griseus), Atlantic puffins (Fratercula arctica), and northern gannets

(Morus bassanus) are also susceptible to entrapment in gillnets and other fixed gear (Tasker et al.

2000). The most applicable influence on common terns in the GOM is the potential depletion and/or displacement of prey near breeding colonies. While no direct evidence of this exists in the GOM, breeding failure and lower adult survival in Arctic terns were associated with changes in fish (prey) availability due to commercial fishing activity in Britain (Suddaby and Ratcliffe

1997 in Kress and Hall 2004).

Availability of prey during breeding may also be influenced by patterns in primary and secondary production. Specifically, many fish species, including common tern prey, have early life stages that rely on interactions with specific, spring zooplankton communities (Longhurst

1995). On the Northeast shelf, Calanus finmarchicus, Pseudocalanus spp., and

Centropagestypicus typicus comprise 75% of the total abundance of zooplankton. C. finmarchicus is one of the most essential zooplankton for upper trophic levels because of its high biomass and significance as prey for early life stages of commercially valuable fish larvae in the

GOM (Sherman et al. 1983, 1987, 1996). The southern part of the GOM is considered the primary source of C. finmarchicus in the region (Sherman et al. 1987, 1988, Meise and O’Reilly

1996).

Nest Density

Over 96% of seabirds breed in colonies, the highest proportion of any bird group

(Coulson 2001). Two benefits of colonial nesting are cooperative defense against predators

(Ashbrook et al. 2010) and information exchange (Weimerskirch et al. 2010). Possible disadvantages include depletion of local food resources (Lewis et al. 2001, Balance et al 2009), increased risk of parasite transmission (Brown and Brown 2004), poor growth rates and body condition of chicks caused by competition for food (Hunt et al. 1986, Lewis et al. 2001, Szostek et al. 2014), and lower reproductive success (Hunt et al. 1986, Forero et al 2002, Schuetz 2011).

Studies of seabird colonies indicate a decline in breeding success as nesting density increases

(Hunt et al. 1986, Stokes and Boersma 2000, Tella et al. 2001).

Phenology

The timing of egg laying in terns varies with age, latitude, food availability, weather, colony, and year (Hays 1978, Smith et al. 1981, Nisbet et al. 1984, Becker et al. 1985, Safina and

Burger 1988, Burger and Gochfield 1991). Breeding requires a considerable amount of energy

(Whittow 2002); therefore, timing should correspond to periods of peak prey availability (Lack

1968, Martin 1987). Timing of breeding has been hypothesized as the reproductive parameter most influenced by climate change (Przybylo et al. 2000, Ramos et al. 2002), as earlier breeding often corresponds to increased productivity in seabirds (i.e., number of chicks raised per pair, clutch size, and chick mass at fledging) (Ramos et al. 2002, Cullen et al. 2009). The North

Atlantic Oscillation (NAO) has correlated with the initiation of breeding and spring migration in multiple studies of birds (Blenckner and Hillebrand 2002, Forchhammer et al. 2002, Huppop and

Huppop 2003) as NAO is a large scale indicator of climatic conditions and may integrate many different aspects of climate compared to local weather variables (Hallet et al. 2004).

The increase in average global temperature, 0.6 °C over the past 100 years, is projected to continue at a more rapid rate (IPCC 1996, Levitus et al. 2000), and the projected effects on plants and animals are expansive across many taxa (Penuelas and Filella 2001, Walther et al. 2002,

Parmesan and Yohe 2003, Root et al. 2003) and ecosystems (Tylianakis et al. 2008), including the marine ecosystem (Hoegh-Guldberg and Bruno 2010). One primary effect among plants and animals is alteration of phenology which has led certain species to modify the timing of major life history events. Several avian studies indicate that earlier breeding times correspond with increasing temperature, and earlier egg laying occurs in years with warmer temperatures

(Parmesan and Yohe 2003, Root et al. 2003, Parmesan 2007, Moe et al. 2009). Long-term advances in laying dates are consistent with global warming data in approximately 60% of studies (Dunn 2004).

Seavey Island Threats

Given that predation and vegetation structure is largely managed at Seavey Island, my general hypothesis is that prey availability and quality, along with nest density and weather, are the most immediate factors influencing common tern productivity on Seavey Island. Climate change poses a long-term threat to both, as it could reduce available nesting habitat, and availability and abundance of prey in the region. The GOM is warming rapidly (Mills et al.

2012, Pershing 2015) and hake species that common terns forage heavily upon are shifting their

distributions northward (Pinksy and Fogarty 2012). If high quality prey is consistently declining in the GOM, then predictably, Seavey Island will likely support a less robust tern population.

In this chapter, I examined the factors that may influence productivity of common terns on Seavey Island. Specifically, I explored the influence of nest density, environmental variables

(i.e., water and air temperature, wind speed, and precipitation), breeding phenology, and prey composition on the reproductive success of common terns and tested the following hypotheses:

1) nest density has a negative relationship with productivity, 2) warmer water temperature and precipitation have a negative effect on productivity, 3) productivity would be higher in nests that were delivered higher quality food items such as hake and herring, and 4) earlier nesting would be correlated with warming GOM water temperatures.

Methods

Productivity

The total number of nesting common terns on White and Seavey Islands has been measured annually with a standardized census conducted similarly on all managed seabird colonies in the GOM during the same time period (Kress and Hall 2004). Productivity was monitored on Seavey Island from 1997-2015 based on methods described by Kress and Hall

(2004), and I analyzed data from 1999-2015. Daily observations of a subsample of nests, hereafter defined as productivity plots, were conducted from 5 blinds located within the nesting colony. A typical blind was an elevated wooden shed-like structure with viewing windows on each side. Productivity plots were established in 2004 by dividing the nesting habitat into grids of unequal size around the blind locations. Daily observations included: date of egg laying, date of hatch, date of fledge, and any associated mortality and/or abandonment of each nesting stage.

Nests were identified by marking adjacent rocks with permanent marker. Eggs in each clutch were labeled with permanent marker (i.e., A, B, or C) and upon hatching, chicks were banded with a United States Geological Survey (USGS) Bird Banding Lab (BBL) band, and the down on their chest was colored with permanent marker according to hatch time (A, B, or C). Chicks were assumed fledged after 15 days post-hatching. Dead chicks were identified by band number.

Productivity equaled the number of chicks fledged divided by the total number of nests

(Kress and Hall 2004). Annual colony production, or the total number of chicks produced, was estimated by multiplying productivity and the total number of nesting pairs. Nonparametric

Mann-Kendall (MK) statistical tests were used to detect trends in total nesting pairs, productivity, and colony production. The test statistic was either S for samples ≤ 9, or Z for samples ≥ 10. Significance values are displayed in the results when a trend was evident, but not when a parameter was stable or absent of trend.

Nest Density

The area of the 14 productivity plots (197.2 m2) was measured using a handheld GPS unit. Annual nest density (nests/m2) was calculated by dividing the number of nests by the area of the productivity plot. The number of nests within plots varied annually from 18 the first year

(1999) to > 200 in later years (2011, 2012, 2014; Table 1-1). Linear regression analysis was used to determine if nest density was related to productivity. A Pearson correlation coefficient was computed to assess the relationship between productivity and nest density using the software

JMP Pro version 13.

Table 1-1. Total number of nests within the 14 monitored productivity plots by year.

Year # of Nests 1999 18 2000 52 2001 135 2002 264 2003 161 2004 164 2005 148 2006 163 2007 145 2008 143 2009 140 2010 179 2011 212 2012 235 2013 190 2014 223 2015 188

Environmental Variables

Relationships between productivity and weather were examined on an annual basis.

Three local weather variables were considered: 1) daily mean water temperature (°C) at 1 m, 2) daily mean air temperature (°C), and 3) daily mean wind speed (m/s). Measurements were obtained for 1 May - 31 August for the years 2002 - 2015 from the Northeastern Regional

Association of Coastal Ocean Observing Systems (NERACOOS) using the Western Maine Shelf

Buoy (43°10’50” N, -70°25’40”W). The buoy is located ~28 km northeast of Seavey Island and was used because it had a more complete time series than a closer buoy. Precipitation data collected in Durham, NH were derived from UNH weather statistics

(http://www.weather.unh.edu/) for the same time period as exact values for Seavey Island were not available.

The entire reproductive season of common terns (May to August) was divided into 3 periods to examine whether productivity is sensitive to environmental variables during a specific portion of the nest cycle: Laying Season, Chick Rearing Season, and Entire Nesting Season. The

Laying Season was defined as the earliest lay date thru the earliest hatch date, the Chick Rearing

Season was the earliest hatch date thru the latest fledge date, and the Entire Nesting Season was the earliest lay date through the latest fledge date for each year. Means were derived from the daily weather variables for each period.

As a proxy for food availability, the abundance of Calanus finmarchicus was used to correspond to the reproductive monitoring period from May through August 1999-2015. This measurement occurred twice monthly at two sampling locations along the coast of New

Hampshire (one site ~ 1.5 km from Great Boars Head and one site ~ 1 km from coast between

Little Boars Head and Rye Ledge) during monitoring by Normandeau Associates for the

Seabrook Nuclear Power Station Monitoring Report (NAI 2015). Linear regression analysis was used to determine if productivity was related to weather variables or the food proxy variable

(JMP Pro version 13).

Prey type

A feeding study conducted on Seavey Island from 1999-2015 documented the 5 most frequently delivered fish species (~70% of observations) to common tern chicks (Terns LLC

2015). Using binoculars, observers in blinds identified and counted the number of prey deliveries during minimum 2-hour observation periods. Observations were focused on nests closest to the blinds as time permitted. Fish species were identified while hanging from adult

bills during transfer to chicks. Data recorded were the time the adult arrived with a prey item, the approximate length of the prey item relative to the bill, identification of the chick when possible (A, B, or C), identification of the parent when possible, and the departure time of the adult. The total number and proportions of prey deliveries were calculated annually (1999-

2015). Small sample size precluded use of data from 2003, 2004, 2010, and 2012. Linear regression analysis was used to determine if productivity was related to prey type or a combination of prey (JMP Pro version 13).

Phenology

Nest monitoring occurred each year beginning when terns initiated laying and continued throughout the season. Initial Lay Date (ILD) was identified by calculating the earliest lay date observed each year. In 2000-2004, lay dates were back calculated from hatch dates using the average incubation date each year. The Final Lay Date (FLD) was defined as the last observed lay date. The duration of laying (DOL) was calculated by subtracting the ILD from the FLD each year. Linear regression analysis was used to identify if a trend occurred in ILD, FLD and

DOL; as they are normally distributed, residuals were checked for normality. The same environmental variables described previously were used to obtain Pearson’s correlation coefficients (JMP Pro version 13) to identify potential relationships between breeding phenology and weather parameters. In addition, annual North Atlantic Oscillation (NAO) data

(https://climatedataguide.ucar.edu/climate-data/hurrell-north-atlantic-oscillation-nao-index- station-based) from 1999-2015 were used to examine possible correlations with the initiation of breeding, as other birds have responded to this large-scale climatic index.

Results

Colony Size and Productivity

Common tern nests were monitored on Seavey Island for 17 consecutive years as part of the restoration effort. During this period, the number of nesting pairs increased from a low of

141 in 1999 (the initial year of monitoring) to a high of 2,881 in 2015. The colony increased rapidly during the first 5 years of restoration. From 2004-2015, there was an increasing trend in nesting pairs (Z = 2.26, p <0.05), followed by stability in the most recent 5 years (2011-2015) (S

= 6; Fig. 1-1). Productivity was highest in the first two years of the restoration when colony size was low, and steadily declined to a low of 0.45 in 2006 (S = -24, p<0.01); productivity was stable with an average of 1.11 in 2007-2015 (S = -10; Fig. 1-2).

3,250 3,000 2,750 2,500 2,250 2,000 1,750 1,500 1,250 1,000 750 500 Total Total Number of PairsNesting 250 - 1999 2001 2003 2005 2007 2009 2011 2013 2015 Year Figure 1-1. Annual number of nesting pairs and level of stability (---) of common terns on Seavey Island 1999-2015.

2.50

2.00

1.50

1.00 # chicks fledged/nest # chicks 0.50

0.00 1999 2001 2003 2005 2007 2009 2011 2013 2015

Year

Figure 1-2. Annual productivity (sum of chicks fledged/sum of nests) and recent level of stability (---) of common terns monitored for productivity on Seavey Island 1999-2015.

Annual Colony Production

A significant increasing trend in annual colony productivity occurred throughout the time series (Z = 2.51, p < 0.05; Fig. 1-3). An estimated 38,038 chicks fledged on Seavey Island over the 17-year monitoring period. There was no trend in chicks produced from 1999-2006, and annual production was stable during 2007-2015 (S = -2) averaging 2,883 number of chicks.

5000

4500

4000

3500

3000

2500

2000

Number chicks of Number 1500

1000

500

0 1999 2001 2003 2005 2007 2009 2011 2013 2015 Year

Figure 1-3. Annual colony production and level of stability (---) of common terns on Seavey Island 1999-2015.

Nest Density

Nest density was lowest at the beginning of monitoring (0.09 and 0.26 nests/m2 in 1999 and 2000) when reproductive success was highest (0.82 and 0.75). A significant negative relationship was found between nest density and productivity (r2 = 0.33, df = 16, p = 0.02) (Fig.

1-4). However, this relationship was heavily influenced by the first two years of restoration, and with these years removed, the relationship was not significant (r2 = 0.0004, df = 14, p = 0.94).

There was a significant negative correlation between productivity and nest density (r = -0.52, df

= 16, p = 0.03).

1.6 2.50

1.4 2.00 1.2

1 1.50 2 0.8

Nests/m 1.00 0.6 # Fledge per per nest # Fledge

0.4 0.50 0.2

0 0.00 1999 2001 2003 2005 2007 2009 2011 2013 2015 Year Nests/m2 # Fledge per Nest

Figure 1-4. Annual nest density (sum nests in plots/sum of plots) and productivity of common terns on Seavey Island 1999-2015.

Environment and Productivity

None of the environmental variables were related to productivity parameters during the laying period, chick rearing period, or entire nesting season (p<0.05, Table 1-2) with a single exception. Precipitation was significant p = 0.05 during the laying period, whereas other variables were not significant (p>0.16).

Table 1-2. Single linear regression coefficients of environmental variables and common tern productivity during the laying, chick rearing and entire nesting periods on Seavey Island NH. Values in bold indicate significance at p = 0.05 level.

Time period Laying period Chick Rearing Entire Nesting Variable r2 p r2 p r2 p Avg Water Temp 1m 0.055 0.42 0.002 0.88 0.003 0.85 Avg Daily Air Temp (°C) 0.159 0.16 0.007 0.78 0.001 0.91 Avg Daily Wind Speed (m/s) 0.005 0.81 0.102 0.27 0.108 0.25 Avg Precipitation (inches) 0.275 0.05 0.010 0.73 0.117 0.23

Prey Type

The five most delivered prey species (n = 7,973) were hake (n = 3,173), herring (n =

1,395), sandlance (n = 364), butterfish (n = 301), and euphausiid shrimp (Meganyctiphanes norvegica, n = 262) (Fig. 1-5). Hake included 3 species combined that were indistinguishable in the field: white hake (Urophycis tennuis), silver hake (Merluccius bilinearis) and four-beard rockling (Enchelyopus cimbrius) (Hall et al. 1999). Unknown fish/items accounted for 1,390

(17%) observations. There was a negative relationship (r2 = 0.480, df = 12, p = 0.01) between euphausiids and productivity. The combination of butterfish and euphausiids was also negatively related (r2 = 0.46, df = 12, p = 0.01) to productivity. No single or combination of prey species was positively related to productivity (Table 1-3).

Figure 1-5. Annual proportions of five most delivered prey by year to common tern chicks during the feeding study on Seavey Island 1999-2015.

Table 1-3. Linear regression coefficients between prey species and reproductive success on Seavey Island NH. Values in bold indicate significance at p = 0.05 level.

Prey fish r2 p hake 0.000 0.97 herring 0.001 0.94 butterfish 0.046 0.48 sandlance 0.053 0.45 euphasid 0.480 0.01 hake & herring 0.000 0.94 hake & butterfish 0.019 0.65 hake & euphasid 0.162 0.17 hake & sandlance 0.011 0.73 butterfish & euphasid 0.465 0.01

Phenology

Common terns initiated laying as early as 20 May (Julian day (JD) =140) and as late as

29 May (JD = 149). The initial lay date (ILD) has occurred earlier since 2000 (r2 = 0.33, df = 15,

p = 0.02, Fig. 1-6). The absolute difference in ILD from 2000 to 2015 was 10 days; the

predicted change was -5.63 days. The ILD was not significantly correlated with any environmental variable (Table 1-4). Common terns concluded laying as early as 20 June (JD =

171) and as late as 1 August (JD = 213), with the final lay date (FLD) occurring 25 days later since 2000 (r2 = 0.28, df = 15, p = 0.03, Fig. 1-7).

152 y = -0.3735x + 147.8 150 R² = 0.33 148

146

144

142 Day of Year of Day 140

138

136

134 2000 2002 2004 2006 2008 2010 2012 2014 Year Figure 1-6. Initial lay date of common terns from nests monitored for productivity on Seavey Island 1999-2015.

220

210

200 y = 1.1985x + 185.25 R² = 0.284 190 Day of Yearof Day 180

170

160 2000 2002 2004 2006 2008 2010 2012 2014 Year

Figure 1-7. Final lay date of common terns from nests monitored for productivity on Seavey Island 1999-2015.

Table 1-4. Pearson correlation coefficients between the initial lay date (ILD) of common terns and environmental variables during the laying period. No environmental variables were significantly correlation with ILD.

Environmental Variable r p value Annual NAO Index -0.120 0.68 Calanus finmarchicus (1000 m3) 0.271 0.35 During Laying period Average Water Temperature (1 meters) 0.084 0.78 Average Precipitation (inches) 0.071 0.81 Average Daily Air Temperature (°C) 0.108 0.71 Average Daily Wind Speed (m/s) -0.187 0.52

The duration of laying (DOL) increased over time (r2 = 0.43, df = 15, p = 0.006; Fig. 1-8), extending by 23.5 days since 2000. The DOL was positively correlated with the annual NAO

Index (r = 0.606, df = 13, p = 0.02). No relationship was found between DOL and the abundance of C. finmarchicus, average water temperature, average precipitation, average air temperature, or average daily wind speed during the laying period (Table 1-5).

Table 1-5. Pearson correlation coefficients between duration of laying (DOL) of common terns and environmental variables during the laying period. Correlation coefficients in bold indicate significance at the p = 0.05 level.

Environmental Variable r p value Annual NAO Index 0.606 0.02 Calanus finmarchicus (1000 m3) -0.383 0.18 During Laying period Average Water Temperature (1 meters) -0.286 0.32 Average Precipitation (inches) 0.057 0.85 Average Daily Air Temperature (°C) -0.197 0.50 Average Daily Wind Speed (m/s) 0.330 0.25

80 y = 1.57x + 37.45 70 R² = 0.43

30 Number Days of Number 20

0 2000 2002 2004 2006 2008 2010 2012 2014 Year

Figure 1-8. Duration of laying period (DOL) (with trend line) of common terns from nests monitored for productivity on Seavey Island 1999-2015.

Discussion

Colony Size and Productivity

The high productivity levels (average 1.67 chicks fledged/nest, Fig. 1-2) measured during the first 5 years of restoration at Seavey Island was consistent with a comparative study of newly established and older colonies in Massachusetts (Tims et al. 2004). Higher productivity, clutch sizes, and chick growth rates in the new colony presumably reflected the influence of proximate and optimal food availability (Tims et al. 2004). Breeding success stabilized following the initial increases on Seavey Island, perhaps due to competition for local food resources and nest sites which are known to influence breeding success of other seabirds (Lewis et al. 2001, Nisbet

2002).

Early in the restoration effort, productivity (chicks fledged/nest) was high but relatively few chicks were produced due to the low number of nesting pairs (Fig. 1-1, 1-2). After increased productivity in subsequent years, productivity stabilized along with annual colony production

(number of chicks produced) (Fig. 1-3). Therefore, simply reporting the productivity rate of monitored nests does not necessarily account for annual recruitment into the population.

Although annual colony production is not typically reported (GOMSWG 2015), it may be a better gauge of restoration goals in newly established colonies. Additionally, estimating total production of chicks for each colony is informative not only for management, but also public relation efforts. The total number of chicks produced (e.g., 1,700) in a colony is more easy to understand than productivity rate (e.g., 0.85 chicks fledged/nest).

Trends in productivity and annual colony production correlate with each other later in the time series and have stabilized since 2007. At some point, an optimal colony size is reached, but

because birds continue to be attracted and settle in the colony, colony size increases beyond that level (Cabot and Nisbet 2013). It’s possible that the carrying capacity of Seavey Island has been reached and the recent annual variability may reflect expected dynamics in carrying capacity

(Mills 2012). Further, local carrying capacity has likely fluctuated as many fish stocks have shifted in distribution further offshore in search of optimal water temperature (Nye et al. 2009).

Presumably, these fish also experience food shortages from regional declines in zooplankton

(Pershing et al. 2015) due to reductions in primary productivity (Balch et al. 2012). Numerous studies implicate scarce abundance of preferred food with reduced breeding success of seabirds

(Montevecchi 1993, Phillips et al. 1996, Frederiksen et al. 2005, Furness 2007). Seabird colonies in the GOM have experienced lower productivity recently due to changes in prey availability (Kress et al. 2016).

The 5-year average (2011-2015) of common tern productivity on Seavey Island is lower than at the three closest colonies: Stratton, Jenny Island, and Outer Green Island (GOSMWG

2016). Stratton and Jenny Islands have experienced increasing numbers of common terns, while

Outer Green Island has remained stable. This difference supports the hypothesis that the Seavey

Island population may be above its carrying capacity that could be limited by nest density, local resources, and/or available nesting habitat.

Nest Density

As hypothesized, there was a negative relationship with nest density and productivity, which was consistent with other studies of seabird colonies (Hunt et al. 1986, Stokes and

Boersma 2000, Tella et al. 2001, Fig. 1-4). Populations may not experience negative density dependent effects until they reach carrying capacity, at which time the rate of growth declines

(Fowler 1981, Sibly et al. 2005). Further, kleptoparisitism and aggression increase with colony

size and nest density, negatively affecting chick survival and productivity (Ludwigs 1998,

Sudmann 1998, Stokes and Boersma 2000, Ramos 2003, Ashbrook et al. 2008, Ashbrook et al.

2010). Lower productivity rates have been observed in recent years on Seavey Island which corresponds with larger colony size (Fig. 1-1, 1-2). Overall colony size, not the density of nests, influenced productivity of common terns, because of resource depletion and food competition

(Szostek et al. 2014). As discussed, Seavey Island is likely at or above carrying capacity and will also probably experience lower productivity from the effects of climate change that include continued dispersal of forage fish in the GOM and worsening severe storm events.

When the first 2 years of productivity on Seavey Island were removed from the analysis, there was no negative relationship between nest density and productivity (Fig. 1-4). But, it is challenging to identify one individual parameter that consistently determines productivity as it is an extremely complex process. Szostek et al. (2014) found that reproductive success of common terns was related to overall colony size not nest density, with resource depletion and food competition as the major influences. Competition among conspecifics accounts for food depletion around the colony and is an important predictor of colony size (Furness and Birkhead

1984, Griffin and Thomas 2000). The colony size on Seavey Island has essentially stabilized

(Fig. 1-1), suggesting that food or availability of nesting habitat are limiting factors. Wooller et al. (1992) found that density dependent competition for food was the most consistent limitation for seabird populations during the breeding season.

Efforts to reduce nest density and expand the rock-vegetation interface habitat have occurred on Seavey Island through the use of prescribed fire in 2006 and 2014 (Terns LLC

2015). Multiple vegetation management techniques are used on many seabird colonies in the

Northeast to expand the open area nesting habitat. However, successful techniques vary among

colonies given the vast differences in substrates and plant communities on islands (Lamb 2011).

An experiment with controlled burning and artificial weed barriers (muslin fabric and artificial turf) found that burned plots quickly regrew after laying and did not remain open for the duration of the nesting season in southern GOM. This lead to nearly complete nest failure and reduced hatching and fledging success of common terns compared to the untreated areas of the colony

(Lamb 2014). The most successful options for providing nesting habitat throughout the entire season are habitat construction techniques (i.e., weed barriers and filling; Lamb 2015). A combination of techniques often produces sustained effects throughout the breeding season

(Burbidge 2008).

Environment and productivity

Changes in weather patterns affect population dynamics of seabirds either through adult survival or productivity and recruitment (Sandvik et al. 2012). As it is difficult to control for factors such as age of adults, experience, and nest location, determining direct effects of weather on breeding seabirds is challenging (Schreiber 2002). However, offspring production was the fitness component most responsive to climatic variability (NAO index) in an analysis of approximately 30 seabird species in the North Atlantic (Sandvik et al. 2012). Average precipitation was related to productivity during the laying period (Table 1-1), possibly because heavy rainfall events can reduce breeding success of common terns prior to egg laying, as females need to gain a considerable amount of weight during this time period and terns do not fish effectively in the rain (Becker et al. 1985). Chick mortality was documented following heavy rain events and major storms on Seavey Island in multiple years (Terns LLC 2008, 2014,

2015). Therefore, the fact that precipitation was correlated with productivity only during the laying period and not the chick rearing period was surprising (Table 1-1). Perhaps mortality

during chick-rearing is largely associated with short-term weather events that were masked in the longer periods I examined. Severe storms are forecasted to increase as a result of climate change

(Easterling et al. 2000, Trenberth 2011), which would presumably increase the frequency of catastrophic events.

Furthermore, it is challenging to identify evidence of weather impacts on seabirds

(Chambers et al. 2015, Satterthwaite et al. 2012, Sandvik and Erikstad 2008) as their responses vary locally (Gaston et al. 2005, Irons et al. 2008, Shultz et al. 2009) and the extent varies among different seabird taxa (Durant et al. 2004, Sandvik and Erikstad 2008, Sandvik et al. 2008)..

Additionally, the ability to recognize weather impacts may be hindered by the length of the study period (Chambers et al. 2015).

Prey Type

Prey delivery to Seavey Island corresponded with diet studies of five colonies in the

GOM, and two others on Seavey Island in which hake and herring were the most delivered prey

(Hall et al. 2000, Blessing 2006, 2007, Fig. 1-5). Hall et al. (2000) found high pollock

(Pollachius virens) delivery in Maine, but on Seavey Island it was minor. Terns delivered a higher proportion of euphausiids than documented by Hall et al. (2000), suggesting that this food is more abundant around Seavey Island. Higher delivery of euphausiids has also been documented on Machias Seal Island in Maine (Black 2006).

There was a negative relationship between euphausiid delivery and productivity on

Seavey Island (Table 1-3), presumably because of its lower energetic value; ~20% less than that of several fish species (Prince & Clarke 1980). Euphausiid delivery may represent behavior of younger, inexperienced terns breeding for the first or second time. Limmer and Becker (2009)

found that younger birds deliver a higher percentage of prey with low energy content and have lower breeding success than experienced breeders. Because age of adult terns on Seavey Island was unknown, I could not evaluate this relationship.

In a feeding experiment with common tern chicks fed three different diets (herring, three- spined sticklebacks (Gasterosteus aculaeatus), and common shrimp (Crangon crangon), the group consuming shrimp (same class of crustaceans Malocostraca as euphausiids) had the lowest growth rate (Becker and Massias 1990). Similarly, when hand-rearing common terns, Gochfield

(1978) found that a diet of crustaceans was inadequate to achieve adequate growth. Herring are the most energetically valuable species during chick development, yet crustaceans provide temporary relief to maintain body mass when availability of high quality fish is low (Becker and

Massias 1990).

In this study, there was a negative relationship between productivity and the combined delivery of euphausiids and butterfish; however, this relationship was largely driven by the relationship with euphausiids (Table 1-3). This was not surprising given the low energetic value of euphausiids (Prince and Clarke 1980) and butterfish are very deep-bodied fish that chicks have difficulty consuming. Increased delivery of these fish to puffin colonies in Maine was associated with declines in chick condition and productivity during years when optimal prey was less available (Kress 2014). Although some species can/will modify their diet in response to reduced resource availability (Suryan et al. 2000, Pinaud et al. 2005, Pettex et al. 2012), other species including common terns may prove incapable (Mattern et al. 2007, Kotzerka et al. 2011).

Phenology

The ILD on Seavey Island is generally occurring earlier and the FLD is extending later in the year, thus the DOL is increasing (Fig. 1-6, 1-7, and 1-8). In 2015, the ILD occurred 10 days earlier than in 2000, yet was not correlated to any environmental factor; however, DOL was positively correlated to the NAO index. Earlier laying time is occurring with numerous species of birds and has been linked with increased ambient temperature (Crick and Sparks 1999,

Parmesan and Yohe 2003; Root et al. 2003; Parmesan 2007; Moe et al. 2009). Breeding dates of

Arctic terns in Denmark have also occurred earlier, and are explained by an increase in spring temperature and the NAO index in May (Møller et al. 2006).

Common terns may potentially lay earlier and extend the laying season in an attempt to align hatching of young with peak food availability, given that the GOM is warming at a rapid rate (Mills 2013); other species in the GOM have shifted reproductive seasons to align to food availability (Richards 2012). Safina and Burger (1985) found that abundance of prey fish was highest when adult terns were feeding chicks, declining later in the season. Response to environmental cues at their wintering areas may influence terns to arrive earlier; unfortunately, first arrival date on Seavey Island isn’t recorded annually. Birds that winter in areas far from their breeding area, as common terns do, may rely on larger scale cues that are variable and difficult to identify (Both and Visser 2001, Sanz et al. 2003). The NAO correlated with the initiation of breeding and spring migration in many studies of birds wintering far from their breeding grounds (Blenckner and Hillebrand 2002, Forchhammer et al. 2002, Huppop and

Huppop 2003, Frederiksen et al. 2004), but not with resident species that tend to be influenced by local conditions near the breeding colony (Frederiksen et al. 2004). Common terns migrate a

great distance to their breeding grounds in the GOM and responded to large-scale climatic signals of NAO, not local weather patterns in the GOM (Table 1-4, 1-5).

Although the phenology data on Seavey Island comprises 15 continuous years, it’s a relatively short time series. Chambers et al. (2015) found that time series based on chronology, which vary less year-to-year, were more likely to reveal trends with fewer years of monitoring than other commonly measured biological variables. The ILD and FLD should continue to be monitored on Seavey Island to verify suspected trends. For most species it is challenging to consider if the advancement was due to climate change or other environmental changes (Both et al. 2004); combined effects is a more plausible explanation. Common terns were restored to the

Isles of Shoals through management, and have likely responded to environmental fluctuations in recent years, possibly caused by reduced prey availability.

Findings and Recommendations

1) The number of nesting pairs on Seavey Island increased rapidly during the first 5

years of the restoration effort, but has stabilized in the last 5 years with an annual

average of 2,752 pairs.

2) Productivity was highest in the first two years of restoration when colony size was

low, steadily decreased to a low of 0.45 fledged/nest in 2006; productivity has been

reasonably stable in 2007-2015 fluctuating from 0.71 to 1.66 fledged/nest.

3) An estimated total of 38,038 chicks were fledged on Seavey Island during the 17-year

monitoring period. There was a general increase in annual productivity from 1999-

2007, but has stabilized since 2007 with an annual mean of 2,883 chicks.

4) It’s possible that the carrying capacity of Seavey Island has been reached with the

recent annual variability reflecting expected dynamics in carrying capacity. Local

carrying capacity has likely fluctuated as many fish stocks have shifted in distribution

further offshore in search of optimal water temperature.

5) The five most delivered prey species were hake, herring, sandlance, butterfish, and

euphausiids. There was a negative relationship between productivity and euphausiids

and euphausiids and butterfish combined. No species of prey was positively related

to productivity, singularly, or combined

6) Common terns are laying earlier and extending the laying season longer.

7) Monitoring of chick growth isn’t conducted on Seavey Island; however, these data

can provide valuable information about local food availability because unusual

fluctuations in chick mass can indicate dietary restrictions.

8) Managers should report annual colony production and productivity to best achieve the

overarching goal of colony restoration of common, roseate, and arctic terns on Seavey

Island. Applying productivity from the sampled plots to the total number of nesting

pairs is an indicator of overall colony “health”, especially in a newly established

colony.

9) A known age and sex subsample of adults should be established to best evaluate adult

feeding rates, species delivery, nest attendance, colony fidelity, and productivity.

10) An effort to reduce the proportion of unidentified prey items in the feeding study

should be conducted. Camouflaged video cameras placed by nests could be used to

monitor prey delivery. A preliminary trial on Seavey Island indicated that the birds

were undisturbed by the cameras.

CHAPTER 2

FORAGING AREA IDENTIFICATION OF BREEDING COMMON TERNS ON SEAVEY ISLAND NEW HAMPSHIRE

Introduction

Techniques used to track movements of common terns include geolocators, very high frequency (VHF) radio tags, and the recent development of a lightweight Global Positioning

System (GPS) tag. Geolocators have been deployed on common terns (Egevang et al. 2010,

Nisbet et al. 2011), but their location accuracy is low (0.5–200 km) (Wilson et al. 2002, Phillips et al. 2004) and attachment can be harmful (Nisbet et al. 2011). VHF radio-tags are lightweight, but aerial tracking via small plane is sometimes necessary, which is both weather dependent and costly (Black 2002, Bugoni et al. 2005, Rock 2007). Recent technology that utilizes a network of receiving towers (MOTUS network) to log radio-tagged animals are increasingly used for migration and stop-over studies along the east coast (Taylor et al. 2017), and have been deployed on terns to examine departure dates and stop over areas in the GOM (Loring et al. 2017).

Receiving towers are costly and require maintenance; therefore, researching local movements without a network of towers requires substantial funds.

Although too large to deploy on most seabirds (Wilson et al. 2002), GPS data loggers are used on larger seabirds such as Cape gannets (Morus capensis), African penguins (Spheniscus demersus), and albatrosses (Thalassarche spp.) (Gremillet et al. 2004, Ryan et al. 2004, Phillips et al. 2007). Recent development of small GPS data loggers has provided for deployment on terns. For example, Mcleay et al. (2010) successfully tagged 21 adult crested terns (Sterna bergii) in Australia to study foraging behavior and habitat use, and more recently Fijn et al.

(2017) used GPS loggers to identify foraging habitats of sandwich terns (Thalasseus sandvicencis) in the Netherlands. GPS technology allows finer-scale tracking with higher accuracy (typically < 5 m) compared to geolocators or radio-tags (von Hünerbein et al. 2000,

Hulbert and French 2001). A disadvantage of small GPS data loggers is the need to recapture the marked bird to download data; however, more recent technology allows remote downloads to base stations (Fijn et al. 2017).

Attaching an electronic tracking device on any animal poses a risk to their immediate wellbeing and overall fitness. It also raises ethical issues concerning impairment of behavior, physiology, breeding success, and energetics (Hawkins 2004, Wilson and McMahon 2006,

Thaxter et al. 2015), and whether data are a representative, unbiased sample of their true behavior (Vandenabeele et al. 2011). Reproductive performance parameters are often used to examine effects of data loggers on seabirds (Vandenabeele et al. 2011) and have been assessed in studies with common and roseate terns in the GOM (Black 2002, Rock 2005).

At-sea foraging ecology of seabirds is largely unstudied (Hall et al. 2000, Granadeiro et al. 2002, Shealer 2002), yet is important to identify principal foraging areas of common tern colonies in the GOM as it undergoes rapid changes in temperature and fish availability (Nye et al. 2009, Mills et al. 2013, Perching et al. 2015). Kress and Hall (2004) and Deluca (2006), emphasized the importance of identifying principal foraging sites for major tern colonies in the northeast to best inform management decisions and protect critically important areas. The need to protect these areas intensifies as marine exploitation by humans is considerable and expanding

(e.g., fisheries, oil and gas, shipping and boating traffic, windfarms) (Syvitski et al. 2005,

Halpern et al. 2008). Recent management efforts to conserve valuable marine environments were achieved through establishment of Marine Protected Areas (MPA) (Kelleher 1999, Sumaila

et al. 2000, Beddington and Kirkwood 2005, Ludynia et al. 2012), and knowledge of seabird foraging ranges is useful in defining candidate MPAs (Thaxter et al. 2012). Past observations indicate that terns forage in the Piscataqua and Merrimack Rivers, and Great Bay; however, exact foraging locations are unknown. Further, little is known about critical foraging, staging, and wintering areas that would help establish a more complete understanding of their vulnerabilities and related conservation opportunities in the GOM (DeLuca 2006).

The objectives of this study were to: 1) test and refine as necessary, an attachment method for GPS data loggers deployed on similar-sized seabirds on common terns, and 2) identify the locations of important foraging areas of breeding common terns in NH.

Methods

Common terns were captured during the 2014 and 2015 breeding seasons using a modified treadle trap placed over the nest (Weller 1957). GPS data loggers (Lotek® PinPoint-50,

Lotek Wireless, Newmarket, ON) were deployed on adults incubating 2-3 eggs during the late incubation stage when adults are restoring lost energy from migration, mate selection, courtship, and egg laying. After mate selection, the male provides food to the female during courtship feeding and egg laying, as the female only leaves nest to bathe or drink until the full clutch is laid

(Nisbet 2002). GPS data loggers weighed 2.6 g after a waterproofing agent was applied, and were <5% of adult body weight (mean weight = 126 ± 6 g) and less than the recommended threshold for birds (Cochran 1980, Caccamise and Hedin 1985). The data loggers stored locations (latitude and longitude) at 15 min intervals (except 1 tag which was programmed at 10 min) and the date, time, and strength of the satellite signal; loggers were programmed to begin recording 1 h post-capture. They were attached to nesting birds within productivity plots in order to compare reproductive success of tagged and untagged (control) birds. Productivity plots

were a subsample of nests near 5 observation blinds that were monitored daily (see Chapter 1).

The birds were recaptured to retrieve the data.

Attachment Method

In 2014, six GPS data loggers were attached with glue and Tesa® tape following methods described in other studies (Ryan et al. 2004, Freeman et al. 2010, Kotzerka et al. 2010, Mcleay

2010, Péron and Grémillet 2013). Because this method proved unsuccessful, a different approach was used in 2015. In addition to the new attachment method, other alterations in the data logger design were made by the manufacturer (Lotek Wireless, Newmarket, Ontario) to reduce the keel as it provided a pivot point that allowed the logger to move on the terns back.

Combinations of data loggers with and without a keel were used in 2015. Each data logger was capable of storing a minimum of 50 locations at designated intervals.

In 2015, 23 GPS data loggers were attached using 2 subcutaneous veterinary grade sutures on the dorsal side approximately 2.5 cm below the neck. Body weight (g) and length of head, culmen, and wing (mm) were measured prior to attachment and birds were marked with a unique color (Sharpie® marker) on their cheek for field identification purposes. All were banded with a USGS metal band on the right leg and a field-readable band on the left leg. Further, these data loggers stored additional locations (upwards of 120) due to the redesigned software. The attachment protocol and handling techniques were approved by the UNH Institutional Animal

Care and Use Committee (IACUC # 140101) (Appendix A).

Data Logger Effect

Nesting birds were captured within productivity plots to compare reproductive success of common terns with and without (control) a GPS data logger. This analysis included the 23 birds

tagged in 2015 to control for any annual influence on productivity (e.g., food availability, weather, predation). Control birds were chosen after the field season from data from productivity plots from a random sample of 23, 2-3 egg nests, with the same lay date range as the tagged birds. Analysis of variance (ANOVA) was used to test for differences among treatments, and mean comparisons were made using Dunnett’s Method in JMP pro version 13.

Foraging Trips

All data from the GPS loggers were censored to remove timestamps prior to and following attachment and removal. All individual data were combined to create a geodatabase in

Environment (Version 0.7.3.0). For each location, speed was calculated by dividing step length by minutes to next location.

Analyses of foraging trips only included the 23 birds tagged in 2015 to avoid any annual influences. Four of the data loggers (2015) were removed from the analysis due to malfunctions.

Trips were identified as foraging based on low speeds (i.e., < 15 km/hr) as in other foraging studies (Awkerman et al. 2005, Weimerskirch et al. 2005, Mcleay et al. 2010). There were 3 categories of foraging trips: 1) complete (starting and ending fix on Seavey Island with minor missing segments (≤ 30 min), 2) nearly complete (last fix in foraging area) and, 3) incomplete when large gaps (≥ 45 min) occurred within the foraging area or commute (Fijn et al. 2017).

Incomplete trips were often the result of poor signal strength, the trip exceeded the programmed time of the data logger, or the battery died. Nearly complete trips were extrapolated by drawing a straight return line to the colony from the last location in ArcGIS. Foraging location was identified using complete, near complete, and incomplete trips. Incomplete trips were only

included if foraging behavior (low flight speeds) occurred. Total trip length (sum of all step lengths for each trip) of complete and near complete trips were used in analysis, with the assumption that the distance was conservative. Trip duration (total elapsed time from onset to return) and average foraging speed (step distance divided by elapsed time between successive locations) were derived from completed trips only. The maximum foraging distance (straight line distance from colony to furthest location) was measured for all terns in all categories.

Results

Attachment Method

Six GPS data loggers were deployed in 2014 using glue and Tesa tape (Figure 2-1); of 3 recovered, 1 malfunctioned, 1 had all locations on the island (Appendix B, Fig. 1), and 1 had 2 incomplete foraging trips (Appendix B, Fig. 2). The reason for tag loss in 50% of birds is unknown; however, one tern was observed with the data logger hanging from its bill by the tape, suggesting it had removed the tag. Due to the low retention rates and loss of data loggers in

2014, 23 data loggers were attached with the suture method (Fig. 2-2) in 2015. All were recovered with 2 malfunctioning and 2 operating <1 h post-deployment. A total of 1,202 GPS locations were recorded by the remaining 19 data loggers.

Total handling time (capture to release) for both attachment methods was similar: 10 to

22 min (avg. = 14 min) with the glue and tape method in 2014, versus 12 to 26 minutes (avg. =

16 min) for the suture method in 2015. The difference in body weight between attachment and recapture ranged from -18 to +10 g, averaging -2 g in 2014 and 2015 combined. The 2014 data loggers recorded 90 fixes for a total of 44.4 h, and the 2015 data loggers recorded 1,202 fixes for

428.8 h (Table 2-1).

Figure 2-1. Picture of common tern with GPS data logger attached with glue and Tesa tape before release (left) and with GPS logger removed (right) in 2014 on Seavey Island, NH.

Figure 2-2. Picture of common tern with GPS data logger sutured on back before release (left) and common tern sitting on nest with GPS data logger sutured on back (right) in 2015 on Seavey Island, NH.

Table 2-1. Tagging information for individual common terns fitted with GPS data loggers in 2015 on Seavey Island, NH.

Fix Time Tag Weight Handling Recapture Mass Number of Bird ID Interval Attached (g) Time (min) Weight (g) Difference Locations (min) (Hours) COTE03 112 0:14 15 110 -2 20.25 46 COTE04 114 0:12 15 114 0 19.25 31 COTE05 130 0:24 15 126 -4 20.75 42 COTE06 124 0:17 15 112 -12 26.75 75 COTE07 130 0:13 15 128 -2 24.50 64 COTE08 136 0:12 15 140 4 29.25 83 COTE09 126 0:15 15 128 2 3.00 8 COTE10 128 0:18 15 132 4 23.50 92 COTE11 120 0:15 15 126 6 28.75 71 COTE12 132 0:18 15 128 -4 22.00 58 COTE13 128 0:12 15 122 -6 23.50 60 COTE14 128 0:19 15 118 -10 25.00 91 COTE15 122 0:24 15 132 10 29.50 77 COTE16 140 0:15 15 122 -18 21.75 56 COTE17 120 0:12 15 120 0 24.25 64 COTE18 128 0:26 10 136 8 22.58 129 COTE19 128 0:14 15 122 -6 26.00 42 COTE20 122 0:24 15 122 0 25.50 68 COTE21 134 0:16 15 132 -2 12.75 45

Data Logger Effect

Productivity of common terns with and without (control) GPS data loggers was compared to identify any adverse effect of the data logger. Productivity of terns with data loggers was 0.78

± 0.30 and without was 0.54 ± 0.43 chicks fledged/nest. Productivity was higher in the group wearing data loggers (p = 0.03), indicating no negative effect from short-term deployment. Birds observed in 2015 did not show overt signs of excessive preening or pulling at the data logger; conversely, the glue and tape method used in 2014 caused noticeable preening behavior.

Foraging Trips

All locations (n = 1,202) of the 19 common terns marked in 2015 are displayed in Figure

2-4. Individual maps are provided in Appendix B. Data loggers were attached for a total of

428.8 h in which 50 foraging trips occurred (Table 2-1). The total combined distance traveled was 1,383 km (range = 19 to 174 km) of which 879 km (64%) were presumed foraging trips (n =

31 complete and near complete trips, n = 12 terns) (Table 2-3). The mean trip length was 28 ±

11 km. The mean maximum distance from the colony was 16 ± 5 km and the maximum distance was 24 km (Fig. 8, 12, and 19 Appendix B). Mean trip duration was 102 ± 28 min, ranging from

45 to 150 min, with average speed of 16.8 ± 12.4 km/h (Table 2-2). COTE20 travelled the longest foraging distance (186 km) (Fig. 20 Appendix B), making 5 trips in approximately 26 h.

Common terns foraged most frequently at three locations: the mouth of the Piscataqua

River, an offshore area approximately 20 km East of Seavey Island, and the mouth of the

Merrimack River (Fig. 2-5). Of the 40 foraging trips (n = 17 terns) where the destination was identified, 50% were in the mouth of the Piscataqua River (20 trips by 11 birds), 28% in the offshore area (11 trips by 8 birds), and 13% in the mouth of Merrimack River (5 trips by 4 birds).

Other foraging locations included between the IOS and the NH shoreline (5%, 2 trips by 2 birds), the mouth of Hampton Harbor (3%, 1 trip by 1 bird), and one bird (3%) that traveled ~ 3 km east of IOS and 4 km northwest of IOS (Fig. 2-6).

Table 2-2. Sample sizes and foraging trip characteristics of breeding common terns with GPS data loggers on Seavey Island, NH in 2015.

Maximum # of Near Mean Trip Mean Trip Mean speed Bird ID Incomplete Complete Distance from Trips Complete Length (km) Duration (min) (km/h) Colony (km) COTE03 3 3 - - - - - 9 COTE04 2 2 - - - - - 16 COTE05 1 1 - - - - - 14 COTE06 4 2 - 2 24 ± 13 98 ± 11 14.9 ± 9.3 17 COTE07 2 1 - 1 24 90 15.9 ± 11.7 21 COTE08 5 1 1 3 32 ± 12 143 ± 11 18.7 ± 16.6 24 COTE09 1 1 - - - - - 10 COTE10 4 1 - 3 20 ± 10 95 ± 9 12.9 ± 9.8 13 COTE11 3 2 - 1 33 120 18.1 ± 5.4 18 COTE12 3 - - 3 31 ± 16 100 ± 38 18.6 ± 12.7 24 COTE13 3 - - 3 19 ± 10 70 ± 23 16.6 ± 9.7 14 COTE14 2 2 - - - - - 13 COTE15 2 - - 2 30 ± 3 143 ± 11 12.9 ± 11.9 15 COTE16 3 - - 3 30 ± 12 95 ± 23 19.9 ± 10.0 17 COTE17 2 - - 2 25 ± 4 75 19.9 ± 10.3 14 COTE18 3 1 1 1 26 ± 1 135 12.8 ± 14.0 13 COTE19 1 1 - - - - - 24 COTE20 5 - 1 4 37 ± 13 105 ± 37 19.7 ± 13.6 22 COTE21 1 1 - - - - - 13 Total 50 19 3 28 Mean (± sd) 28 ± 11 102 ± 28 16.8 ± 12.4 16 ± 5 n 31 28 31 19

Figure 2-3. All GPS locations (n = 1,202) collected from 19 common terns with GPS data loggers in 2015 on Seavey Island, NH.

Figure 2-4. The 3 primary foraging areas (n = 21 trips by 12 birds) of common terns with GPS data loggers in 2015 on Seavey Island, NH.

Figure 2-5. Other foraging locations (n= 4 trips by 4 birds) of common terns with GPS data loggers in 2015 on Seavey Island, NH.

Discussion

Attachment Method

Despite previous successful use of the glue and Tesa tape method of attachment with seabirds (Ryan et al. 2004, Freeman et al. 2010, Kotzerka et al. 2010, Mcleay 2010, Péron and

Grémillet 2013) it resulted in low retention rates on common terns in this study. As one tern was observed with the data logger hanging from its bill by the tape, it was likely that birds were able to remove them. Similarly, sandwich terns pulled out feathers to remove data loggers attached with tesa tape (Fijn et al. 2017), additional evidence that this attachment method may be unsuitable for terns. As terns primarily plunge dive for their prey (Nisbet 2002, Cabot and

Nisbet 2013), the force may pull at and around proximate feathers causing discomfort. Moderate feather loss occurred upon removal of the data logger, which might conceivably result in heat loss or infection (Fig 2-1). The suture attachment method was more successful given that no data loggers were lost, and terns did not exhibit excessive preening at the point of placement.

One minor consideration is the slightly increased handling time (2 min) required to complete 2 sutures; however, common terns tend to be more tolerant of handling than other tern species

(Nisbet 1981). Sutured radio-tags, which are lighter than GPS data loggers, has proved effective on terns in the GOM (Cranmer et al. 2017, Loring et al. 2017).

Data Logger Effect

Attaching data loggers to birds can be detrimental through physical injury, behavioral change, lower flight speed, reduced foraging ability, and in certain cases, lower hatching success

(Wilson et al. 1986, Gessaman and Nagy 1988, Massey et al. 1988, Wanless et al. 1989, Buehler

et al. 1995, Schmid et al. 1995, Wilson et al. 2004, Nisbet et al. 2011). Surprisingly, productivity was higher for common terns wearing data loggers (Table 2-2), indicating no negative effect from the short-term deployments. This might be expected as nests with 2 or 3 eggs in late incubation were selected for attaching data loggers, and older more experienced birds often lay first and have higher reproductive success (Nisbet et al. 1984, Limmer and Becker 2009); however, the treatment and control groups were selected similarly, using the same lay date ranges. Deployments were < 30 h and occurred during incubation when energy expenditure is low relative to the other breeding stages (Walsberg 1983). Klaassen et al. (1992) found that imitation radios mounted on the backs of nesting common terns did not affect daily energy expenditure. Additionally, Black (2002) and Rock (2005) found no difference in productivity in

GOM colonies between common or roseate terns with or without radio tags.

Foraging Trips

Maximum foraging distance of breeding common terns was estimated as 30 km in the

United Kingdom and ~ 20 km at Bird Island, MA (Nisbet 1983, review by Thaxter et al. 2012).

More locally, Black (2002) measured a maximum foraging distance of ~ 30 km (conservative estimate based on a 30 km radius) from Machias Seal Island, New Brunswick, whereas, Rock

(2005) found a much smaller range of 9.4 ± 4.7 km at Country Island, Nova Scotia. In this study, the maximum foraging distance was 24 km by 3 birds all traveling to the mouth of the

Merrimack located 24 km from Seavey Island (Fig. 8, 12, and 19 Appendix B). The mean maximum foraging distance of 16 km from Seavey Island is similar to Nisbet’s (1983) estimate, but less than the mean of 19.8 km observed from Machias Seal Island; however, birds nesting in larger colonies tend to travel further than those in smaller colonies (Erwin 1978, Lewis et al.

2001). Machias Seal Island has a larger and more diverse seabird colony than Seavey Island,

supporting a similar number of terns (3,000 pairs of common and arctic), and approximately

2,800 pairs of Atlantic puffins, 530 pairs of razorbills, 150 pairs of Leach’s storm petrels, and small numbers of common murres (Black 2002). It is also located further from shore (13 km) than Seavey Island, so a longer foraging range is expected. Additionally, in years of low food quality and/or availability, seabirds presumably travel further from colonies (Furness and Tasker

2000). Mean trip lengths (28 km) from the Seavey Island colony was similar to the maximum foraging range from Machias Seal Island; mean trip length is not typically reported in other tern foraging studies.

Aggregations of seabirds are associated with areas of high productivity or accumulation of biological matter such as frontal areas, continental shelfs, or inshore waters (Abrams 1985,

Wahl et al. 1989, Hay 1992, Harrison et al. 1994, Pakhomov and McQuaid 1996, Piatt et al.

2006, Hyrenbach et al. 2007). Similarly, common terns foraged frequently at three primary locations all of which are associated with fronts: the mouth of the Piscataqua River, an offshore area approximately 20 km East of Seavey Island, and the mouth of the Merrimack River (Fig. 2-

5).

The mouth of the Piscataqua River (Portsmouth Harbor) consists of depths to 22 m, whereas the Merrimack River mouth is much shallower (10 m). River mouths are considered density fronts or tidally driven plumes which are formed by the freshwater flow into the ocean coupled with strong tidal mixing, and generally aggregate zooplankton and larval fish (Govoni et al. 1989, Govoni and Grimes 1992, Grimes and Kingsford 1996, Kudela et al. 2010, Kowalczyk et al. 2015) that provide food to seabirds (Skov and Prins 2001, Bost et al. 2009, Zamon et al.

2014, Kowalczyk et al. 2015). Common terns foraged in river mouth areas 63% of the time, and

8 individuals repeatedly visited the same location more than once, behavior consistent with

common terns (Becker et al. 1993) and likely due to the local high abundance of prey. River plumes are identified as important foraging habitats of seabirds (Skov and Prins 2001,

Kowalczyk et al. 2015, Arimitsu et al. 2016) as a result of biophysical coupling near the plume edge which attracts zooplankton (Morgan et al. 2005). These zooplankton-rich waters in turn attract prey of common terns such as hake and herring that consume zooplankton and larval fish

(Garrison and Link 2000, Bachiller et al. 2018, Suca et al. 2018).

Common terns are primarily associated with inshore foraging areas (e.g., bays, inlets, saltmarsh creeks, lakes, ponds, rivers, and shallow coastal waters; Nisbet 2002). Even when nesting on islands ~ 15 km offshore in Maine, they are believed to feed primarily inshore (Hall

1999). However, offshore areas accounted for 28% of the foraging trips from Seavey Island and

2 individuals repeatedly foraged offshore. Little is known regarding the importance of offshore areas to seabirds in the GOM, with the exception of the summer molting grounds of Greater

Shearwaters and Northern Fulmars (Huettman and Diamond 2000, East Coast Aquatics 2011).

Most studies have focused on breeding areas given the inherent difficulty associated with observing foraging seabirds in the open ocean (Black 2002). Common terns have been observed foraging above predatory fish (Safina and Burger 1985, Goyert 2013) including tunas (Thunnus sp.) and dolphins (Delphinus sp.) (Goyert 2013) that occur in the GOM during summer (Walli et al. 2009). The extent to which common terns associate with fishing boats, that are prevalent in the GOM, is unknown.

The offshore foraging area was expansive and tern foraging locations were often associated with steep gradients in bathymetry where extreme mixing occurs in the form of fronts.

Primary production is greater in frontal areas (Franks 1992, Yoder et al. 1994) and like river plumes, support bottom-up effects and aggregations of predators (Decker and Hunt 1996, Russell

et al. 1999, Jahncke et al. 2005). Behavioral patterns of seabirds are linked to biophysical oceanographic processes that influence the availability of prey (Cox et al. 2013, Bertrand et al.

2014, Woodson and Litvin 2015, McInnes et al. 2017), and these areas within the GOM are considered one of the most productive and diverse marine areas in the world (Sherman and

Skjoldal 2002), with unique topography and oceanographic conditions that support extremely productive phytoplankton and zooplankton populations that support large fish populations

(Waring et al. 2002). Foraging by common terns in these offshore frontal areas provides supporting evidence for their protection.

GPS data logger technology identified previously unknown foraging locations of common terns on coastal NH. Since the attachment method failed in 2014, it was impossible to examine for annual differences in habitat use that can occur (Fijn et al. 2017). Further analysis of the location data can possibly inform specific questions about habitat use. For example, seabird foraging activity can be influenced by bathymetry, chlorophyll a, SST, and tidal cycle

(Freeman et al. 2010, McLeay et al. 2010, Chivers et al. 2013). A study combining foraging location with feeding observations during the chick rearing period could assess the relationships among location, prey availability, diet, and energetic balance. The foraging areas, role, and energetic demand of males and females could also be investigated to explore gender differences in reproductive ecology and behavior of common terns. This study has provided important technological information to aid continued research of the reproductive ecology of terns that is imperative given recent and predicted environmental disruptions associated with climate change in the GOM.

Findings and Recommendations

1) The glue and Tesa tape method of attachment used successfully in numerous seabird

studies was not appropriate for use with common terns.

2) The suture attachment method proved successful for short-term deployment given

that no loggers were lost and terns did not exhibit excessive preening at the point of

placement.

3) Common terns foraged frequently at three locations, all of which were associated

with fronts that aggregate zooplankton and larval fish: the mouth of the Piscataqua

River, an offshore area approximately 20 km East of Seavey Island, and the mouth of

the Merrimack River.

4) Common terns foraged in river mouth areas 63% of the time, and 8 individuals

repeatedly visited the same location more than once, as documented in other studies

of common terns.

5) Offshore areas accounted for 28% of the foraging trips of common terns and 2

individuals repeatedly foraged offshore.

6) The maximum foraging distance was 24 km by 3 birds which traveled to the mouth of

the Merrimack River.

7) Since short-term GPS logger deployments were successful and no detrimental effects

on behavior or fitness were documented, similar methods could be used with State

and Federally Endangered roseate terns to study their foraging ecology.

8) Long-term data logger deployments using the suture method could also be attempted

on common and roseate terns to address information gaps regarding threats at

wintering areas, and adult and juvenile survival.

9) The temporal variability presumably associated with foraging behavior and sites

should be investigated with a multi-year study.

10) Attach GPS data loggers to equal numbers of males and females during the breeding

season to identify if they utilize separate or overlapping habitats.

11) Examine the bioenergetics of males and females during the breeding season to

identify if prey availability in the GOM is sufficient.

12) Further study should address foraging ecology during the critical chick-rearing period

to identify temporal patterns in foraging behavior and movement.

13) Foraging areas should be further explored to examine what variables influence tern

forage and foraging (e.g., bathymetry, chlorophyll a concentrations, SST, etc.).

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APPENDICES

APPENDIX A: Institutional Animal Care and Use Committee Approval.

APPENDIX B. Movements of individual breeding common tern with GPS data loggers in 2014 and 2015.

Figure 1. GPS fixes (all on island) of COTE01 that nested on Seavey Island in 2014, NH.

Figure 2. Incomplete trips (n = 2) of COTE02 that nested on Seavey Island in 2014, NH.

Figure 3. Incomplete trips (n = 3) of COTE03 that nested on Seavey Island in 2015, NH.

Figure 4. Incomplete trips (n = 2) of COTE04 that nested on Seavey Island in 2015, NH.

Figure 5. Incomplete trip (n = 1) of COTE05 that nested on Seavey Island in 2015.

Figure 6. Foraging trips (n = 2 complete, 2 incomplete) of COTE06 that nested on Seavey Island in 2015.

Figure 7. Foraging trips (n = 1 complete, 1 incomplete) of COTE07 that nested on Seavey Island in 2015.

Figure 8. Foraging trips (n = 3 complete, 1 incomplete) of COTE08 that nested on Seavey Island in 2015.

Figure 9. Foraging trips (n = 1 incomplete) of COTE09 that nested on Seavey Island in 2015.

Figure 10. Foraging trips (n = 3 complete, 1 incomplete) of COTE10 that nested on Seavey Island in 2015.

Figure 11. Foraging trips (n = 1 complete, 2 incomplete) of COTE11 that nested on Seavey Island in 2015.

Figure 12. Foraging trips (n = 3 complete) of COTE12 that nested on Seavey Island in 2015.

Figure 13. Foraging trips (n = 3 complete) of COTE13 that nested on Seavey Island in 2015.

Figure 14. Foraging trips (n = 2 incomplete) of COTE14 that nested on Seavey Island in 2015, NH ArcMap 10.3.1

Figure 15. Foraging trips (n = 2 complete) of COTE15 that nested on Seavey Island in 2015, NH.

Figure 16. Foraging trips (n = 3 complete) of COTE16 that nested on Seavey Island in 2015, NH.

Figure 17. Foraging trips (n = 2 complete) of COTE17 that nested on Seavey Island in 2015, NH.

Figure 18. Foraging trips (n = 3 complete) of COTE18 that nested on Seavey Island in 2015, NH.

Figure 19. Foraging trips (n = 1 complete) of COTE19 that nested on Seavey Island in 2015, NH.

Figure 20. Foraging trips (n = 5 complete) of COTE20 that nested on Seavey Island in 2015, NH.

Figure 21. Foraging trips (n = 1 incomplete) of COTE21 that nested on Seavey Island in 2015, NH.