2nd World Seabird Conference “Seabirds: Global Ocean Sentinels” 26-30 October 2015 Cape Town, South Africa

ANALYSIS OF MONITORING METHODS OF SEABIRD COMMUNITIES ON RASO ISLET, CAPE VERDE (P2-H-173)

Almeida, Nathalie1; Paiva, Vitor2; Ramos, Jaime2; Geraldes, Pedro3; Fortes ,Isabel1; Melo, Tommy1 ; Rabaça, João4

1Biosfera I, Cape Verde, www.biosfera1.com; 2 Coimbra University; 3 SPEA, Portugal, www.spea.pt; 4 Évora University

Raso Islet is an authentic sanctuary for seabirds; some of them endemic to Cape Verde. In this present work we studied the populations of pelagic seabirds (Procelariiforms) of Calonectris edwardsii (Oustalet, 1883) Cape Verde Shearwaters and Bulwer’s Petrel Bulweria bulwerii, (Jardine & Selby, 1828) from the islet. The current size of the shearwater population is not very well known, as well as the impact of continuous illegal killing of juveniles. Given that the majority of the world population of this species is in Santa Luzia and Branco and Raso Islets MPA, it is essential to know the size of the breeding population (Lecoq, 2009), as well as the Bulwer’s Petrel population since we found no literature related to recent census for the Cape Verde islands.

Cape Verde Shearwater Fig. 1 Ð Geographic location of Raso Islet. Bulwer’s Petrel

From August - November, we used a series of fixed-point circular plots (total plot area = 706.50 m2) In 209 detections of active nests in 2013 (Fig. 3), we obtained NLLR and PVEG as the most counting holes with chicks/parents/eggs of the target species. The islet (Fig. 1) was then mapped significant characteristics (Table 1) for predicting densities of B. bulwerii, as it breeds more in coastal and divided into UTM squares, where 28 plots were randomly distributed in representative areas of ravines and rocky walls in the islet interior, and in areas where there is presence of vegetation, the colonies (Fig. 2) predicting nest densities for a combination of environmental variables functioning as cover for the rocks and cavities where they occur. For C. edwardsii, PVEG is most described, through multiple regression, and then resorted to extrapolation with the colony area to important and significant (Table 2); acting as a form of protection against nest floods, reducing their obtain a population estimate and compare with other data from previous studies. impact and preventing rock landslides, causing chick mortality.

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10 N¼ of nestsN¼ of 5

0 P1 P2 P3 P4 P5 P6 P7 P8 P9 P11 P11 P10 P12 P13 P14 P15 P16 P17 P18 P19 P20 P21 P22 P23 P24 P25 P26 P27 P28 CMYK - blue to green N¼ of Plots Fig. 3 Number of Calonectris edwardsii (Green) and Bulweria bulwerii (blue) nests for each plot.

The average density of C.edwardsii was 0.0794 breeding pairs per 10m-2, representing 79 breeding Fig. 2 ÐCalonectris edwardsii) ; unoccupied areas (brown) ;colonies (yellow) 28 plots (green). pairs ha-1 (12 ± SE). Extrapolating these results with potential nesting areas (~ 351 ha), an average Source: Lecoq, 2009 estimate of 27,869 breeding pairs was established (SE = 4233; 95% CI = 19572-36166). For B. Coefficients Statistics bulwerii we obtained 0.0245 per 10m-2 breeding pairs, i.e. 24 breeding pairs ha-1 (10 ± SE) with an Statistics Coefficients established average population size of 8,600 breeding pairs (SE = 3583; 95% CI = 1577-15623). Final Model SE T P Final β Model β T P SE Although the population density of C. edwardsii and B. bulwerii may have been underestimated due Constant -0,041 0,020 -2,066 0,049 Constant 0,060 0,023 6,326 <0,000 to weather constraints in 2013, the results are much higher from earlier studies, showing that the population has in fact been growing these last few years. However, it remains important to make a VEGP 0,026 0,008 3,172 0,004 VEGP 0,011 0,011 2,057 0,050 new estimate at the start of incubation in order to account for all hatching failure during this period.

NLLR 0,020 0,009 2,102 0,046 For future use, follow-up or repeat counts at the end are also suggested; allowing a real estimate of Table 1 Ð Coefficients and statistics of selected Table 2 Ð Coefficients and statistics of selected pair numbers, as well as quantifying hatching success. The number of plots should also be parameter in the final explaining model of the parameter in the final explaining model of the increased to obtain a sample that is more representative of the colonies. density of Bulweria bulwerii. VEGP Ð density of Calonectris edwardsii. VEGP Ð Vegetation Percentage. NLLR Ð Number of Vegetation Percentage. Large Loose Rocks.

§ For both species we found that the PVEG is important in nesting sites, especially for B. bulwerii as it nests preferably in cavities or between rocks covered by vegetation. NLLR appear to be also selected by the latter; having been found in greater numbers of individuals in areas with this specific characteristic (Hazevoet, 1995). § It is also important to make a habitat selection study at micro-scale / nest scale; measuring and establishing the best features of an ideal nest for breeding, and done in previous studies with C. borealis (Werner et al., 2014; Lecoq, 2010) and B. bulwerii in Azores (Ramos et al., 1997). These studies may enable the construction of artificial nests which may be important in intra- and inter-specific competition studies, reproductive success, progenitor quality and for Shearwater reintroduction in Santa Luzia to potentiate an increase of the population, taking into account that this species only nests in the Cape Verde islands. ACKNOWLEDGEMENTS: BIBLIOGRAPHY: Alcyon for financial support of all work done in Raso Islet Lecoq M (2009) Relatório sobre a ação de formação no ilhéu Raso (Cabo Verde) em Outubro de 2009. Sociedade Portuguesa para o Estudo in Cape Verde Shearwater conservation projects; das Aves; Hazevoet CJ (1995) The birds of the Cape Verde Islands. BOU Checklist 13. British Ornithologists’ Union, Tring; Biosfera for support and the opportunity to work on this Ramos JA, Monteiro LR, Solá E & Moniz Z (1997) Characteristics and competition for nest cavities in burrowing Procellariforms. The Condor 99: project in the islet; Critical Ecosystem Partnership Fund 634-641; (CEPF) for financial support under project No. 61459 Walsh PM, Halley DJ, Harris MP, del Nevo A, Sim IMW & Tasker ML (1995). Seabird monitoring handbook for Britain and Ireland. Published by "Protecting Threatened and Endemic species in Cape JNCC / RSPB / ITE / Seabird Group, Peterborough; Werner AC, Paiva VH & Ramos J (2014) On the “real estate market”: Individual quality and the foraging ecology of male Cory«s Shearwaters. Verde: Phase 1 of a major Island Restoration Project" The Auk, Ornithological Advances, Volume 131, pp. 265-274.

With the financial support of MAVA Foundation

CMYK - blue to green