Survival and dispersal of the Cyprus wheatear Oenanthe cypriaca, an endemic migrant

Will Cresswell,Marina Xenophontos

doi:10.1007/s10336-015-1315-1

Abstract

Many populations of European migrant bird species are declining and this may be driven by survival rates; however, there are few studies that can estimate true survival rates. Cyprus wheatears Oenanthe cypriaca are an endemic migrant that winter in East Africa: populations are probably not declining but are annually variable. We recorded territory occupation and reoccupation in a colour-ringed population of 45–69 pairs over a 4-year period (2010–2013) from April to August to measure apparent survival and determine how it varied with sex, age, breeding productivity and year. We then estimated true survival by correcting apparent survival for dispersal by recording territory shifts and how this also varied by sex, age, breeding productivity and year. Apparent annual survival rate varied significantly by sex, age and year (males 2011, 2012, 2013: 0.70, 0.50, 0.62; females: 0.56, 0.34, 0.47; chicks: 0.35, 0.19, 0.28) but was not affected by the productivity of a territory. An average of 1.1 % of males and 8.2 % of females were lost during breeding, where 5/7 lost females were found depredated during incubation. Adults did not usually change territories between years (87 % were resident and 99 % moved less than four territories between years) regardless of sex, productivity or year; chicks, independent of their sex, moved on average three territories away from their natal territory. After correcting apparent survival for the probability of dispersal, males had the highest true minimum annual survival compared to females which were very similar to chicks (males 2011, 2012, 2013: 0.77, 0.50, 0.65; females: 0.65, 0.35, 0.50; chicks: 0.64, 0.34, 0.49). The results indicate a very high survival rate for a small passerine migrant, although they are probably sufficiently annually variable to profoundly affect annual population dynamics. If females have a lower survival rate, the sex ratio at birth may be female-biased to compensate; alternatively, females may have longer range dispersal than we could measure, particularly if they respond to their mates not returning by moving territories, leading to underestimation of their true survival. A high survival rate may be due to the rarity of sparrowhawks on Cyprus and the wheatears relatively short distance migration.

Highlights

Many populations of European migrant bird species are declining, and measuring survival rates at the different stages in their annual cycle is crucial to understand why this is so (Newton 2004, 2008)
Many populations of European migrant bird species are declining and this may be driven by survival rates; there are few studies that can estimate true survival rates
Our study showed that Cyprus wheatears were highly sitefaithful with little dispersal for adults and dispersal on the scale of only a few 100 m for first-year birds

Summary

Introduction

Many populations of European migrant bird species are declining, and measuring survival rates at the different stages in their annual cycle is crucial to understand why this is so (Newton 2004, 2008). Populations of Afro– Palearctic migrants declined over large parts of Europe between 1970 and 2000, for species wintering in arid open habitats in Africa (Sanderson et al 2006); more recent analyses have identified that species wintering in the Guinea savannah may have greater declines (Thaxter et al 2010; Ockendon et al 2012) The causes of these declines are not well known and are likely to be species-specific; for example, reduced rainfall and, as a result, habitat quality in the wintering grounds (Kanyamibwa et al 1993), habitat quality of stop-over sites (Saino et al 2004; Schaub et al 2005), or phenology mismatch (Both and te Marvelde 2007; Jones and Cresswell 2010). Reproductive efforts can impact adult survival rates (McCleery et al 1996)

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Conclusion