Seasonal survival estimation for a long-distance migratory bird and the influence of winter precipitation

Abstract

Conservation of migratory animals requires information about seasonal survival rates. Identifying factors that limit populations, and the portions of the annual cycle in which they occur, are critical for recognizing and reducing potential threats. However, such data are lacking for virtually all migratory taxa. We investigated patterns and environmental correlates of annual, oversummer, overwinter, and migratory survival for adult male Kirtland's warblers (Setophaga kirtlandii), an endangered, long-distance migratory songbird. We used Cormack-Jolly-Seber models to analyze two mark-recapture datasets: 2006-2011 on Michigan breeding grounds, and 2003-2010 on Bahamian wintering grounds. The mean annual survival probability was 0.58 ± 0.12 SE. Monthly survival probabilities during the summer and winter stationary periods were relatively high (0.963 ± 0.005 SE and 0.977 ± 0.002 SE, respectively). Monthly survival probability during migratory periods was substantially lower (0.879 ± 0.05 SE), accounting for ~44% of all annual mortality. March rainfall in the Bahamas was the best-supported predictor of annual survival probability and was positively correlated with apparent annual survival in the subsequent year, suggesting that the effects of winter precipitation carried over to influence survival probability of individuals in later seasons. Projection modeling revealed that a decrease in Bahamas March rainfall >12.4% from its current mean could result in negative population growth in this species. Collectively, our results suggest that increased drought during the non-breeding season, which is predicted to occur under multiple climate change scenarios, could have important consequences on the annual survival and population growth rate of Kirtland's warbler and other Neotropical-Nearctic migratory bird species.

Diversification of a ‘great speciator’ in the Wallacea region: differing responses of closely related resident and migratory kingfisher species (Aves: Alcedinidae:Todiramphus)

“…Although wintering grounds have strong carry-over effects on breeding success (Bearhop et al 2004, Latta et al 2016, Rockwell et al 2017, and Sacred Kingfisher individuals are known to be faithful to the same wintering site (Woodall & Kirwan 2018b), the ability of the Sacred Kingfisher to adapt to its wintering grounds will be limited by the constraints placed upon the population by the demands of its breeding grounds and its migration route. The Sacred Kingfisher is found in mangrove habitat throughout the region, regardless of island size (but with the addition of the Collared Kingfisher as a potential competitor on smaller islands).…”

The Plight of Migrant Birds Wintering in the Caribbean: Rainfall Effects in the Annual Cycle

“…The sensitivity of the KIWA's population to winter droughts was evident from projection modeling, which indicated that a decrease in Bahamas March rainfall >12.4% from current mean levels could cause the size of the KIWA population to decrease due to winter droughts alone [62]. Further contributing to concerns about rainfall effects on KIWAs and other migrant birds in the Caribbean are predictions of increased occurrence of droughts under multiple climate change scenarios in the Caribbean [63].…”

“…We now recognize that the abundance and distribution of migrant birds are limited by events occurring throughout the annual cycle [16,81] and that events happening in one stage may carry over to influence other stages [20,24,62,70]. Without knowledge of the relative importance of various limiting factors during breeding, migratory, and wintering periods on population dynamics for each species of conservation concern, it will be impossible to implement effective management actions for each of these migrant species [16].…”

“…Monthly survival rates for the male KIWAs were relatively high during the stationary periods of the annual cycle (summer = 0.963 ± 0.01 SE; winter = 0.97 ± 0.01 SE) in contrast to the markedly lower monthly survival rates during the migratory period (0.886 ± 0.05 SE), which accounted for 41% of all annual mortality of adult birds. Using a model selection framework, Rockwell et al [62] also evaluated the influence of multiple climate variables on annual survival of the KIWA. Their analysis indicated that March rainfall in the Bahamas was the best-supported predictor of annual survival probability.…”

“…The data on overwinter site fidelity and annual return of banded KIWAs (2003-2010) combined with the breeding ground site fidelity and annual return data (2006-2011) were used to estimate apparent annual, oversummer, overwinter, and migratory survival for the warbler [62]. These analyses were restricted to males, as sample sizes for females were inadequate for modeling the two mark-recapture data sets.…”