Does seasonality drive spatial patterns in demography? Variation in survival in African reed warblersAcrocephalus baeticatusacross southern Africa does not reflect global patterns

Abstract

Among birds, northern temperate species generally have larger clutches, shorter development periods and lower adult survival than similarly-sized southern and tropical species. Even though this global pattern is well accepted, the driving mechanism is still not fully understood. The main theories are founded on the differing environmental seasonality of these zones (higher seasonality in the North). These patterns arise in cross-species comparisons, but we hypothesized that the same patterns should arise among populations within a species if different types of seasonality select for different life histories. Few studies have examined this. We estimated survival of an azonal habitat specialist, the African reed warbler, across the environmentally diverse African subcontinent, and related survival to latitude and to the seasonality of the different environments of their breeding habitats. Data (1998–2010) collected through a public ringing scheme were analyzed with hierarchical capture-mark-recapture models to determine resident adult survival and its spatial variance across sixteen vegetation units spread across four biomes. The models were defined as state-space multi-state models to account for transience and implemented in a Bayesian framework. We did not find a latitudinal trend in survival or a clear link between seasonality and survival. Spatial variation in survival was substantial across the sixteen sites (spatial standard deviation of the logit mean survival: 0.70, 95% credible interval (CRI): 0.33–1.27). Mean site survival ranged from 0.49 (95% CRI: 0.18–0.80) to 0.83 (95% CRI: 0.62–0.97) with an overall mean of 0.67 (95% CRI: 0.47–0.85). A hierarchical modeling approach enabled us to estimate spatial variation in survival of the African reed warbler across the African subcontinent from sparse data. Although we could not confirm the global pattern of higher survival in less seasonal environments, our findings from a poorly studied region contribute to the study of life-history strategies.

Fecundity selection theory: concepts and evidence

“…However, as can be expected for any macroecological generalization, other studies have also failed to support this rule in a number of cases, including vertebrates and invertebrates (e.g. Yom‐Tov, Christie & Iglesias, ; Jansen et al , ).…”

Rainfall and population dynamics of Grey Pileated Finch Coryphospingus pileatus (Aves: Passeriformes) in a Neotropical dry forest

“…More intriguing than the patterns themselves are the mechanisms that govern them, and their implications for the demography of birds (e.g., Jansen et al 2014). While temperate environments exhibit a seasonal climate driven by temperature luctuations, dry tropics exhibit more unpredictable patterns generally focused around rainfall periodicity (Murphy and Lugo 1986;Dean et al 2009).…”

Factors affecting female space use in ten populations of prairie chickens

“…Replicated population studies of vertebrate species at multiple sites are rare but can provide important insights into local adaptation and evolution of life histories (Sandercock et al 2005, Salgado-Ortiz et al 2008, Bears et al 2009, Jansen et al 2014. Our collaborative analysis is a unique opportunity for a large-scale analysis of the spatial ecology of prairie chickens.…”