Birds with multiple homes. The annual cycle of the pallid swift (Apus pallidus brehmorum)

We tracked pallid swifts (Apus pallidus brehmorum) from a single breeding colony in Gibraltar over two years. Our results show movement of birds between specific regions within the non-breeding geographical area at specific times of the year. The tracking of a single individual showed remarkable fidelity to the areas visited between years. Furthermore, two pallid swifts tracked over the entire eight-month non-breeding period, while in Africa, gave no indication of coming to land, supporting previous findings of an airborne existence in swifts outside the breeding season. In addition, the crossing of the Sahara Desert to and from breeding grounds is remarkably fast, with one individual crossing it in just over a day. We discuss our findings in the context of bird migration evolutionary strategies.

Resurveys Reveal Potential Population Increases of the Himalayan Griffon in Central West Nepal

ABSTRACT The Himalayan Griffon (Gyps himalayensis) is listed as near threatened and its populations are poorly monitored. During late May and early June of 2013, 2014, and 2016, we resurveyed transects that were originally sampled 2002–2006. These transects were within the Annapurna region of Nepal. From 2010 through 2020, we also monitored a breeding colony of Himalayan Griffons within the Arghakhanchi District of Nepal. The number of non-adults, adults, and total Himalayan Griffons counted along the transects approximately doubled from the previous counts. At the colony, the number of breeding pairs and young fledged increased during the study (yearly growth rate [r] = 0.049 and 0.089, respectively). The number of offspring fledged per breeding pair also increased (r = 0.040). Our results are encouraging, but we only surveyed a small portion of the global population and over a relatively short time period. We recommend expanded and coordinated population monitoring for this species across its range.

Physiological condition reflects polymorphism at the toll-like receptors in a colonial waterbird

Toll-like receptors (TLRs) are a crucial component of vertebrate innate immune response. Despite their importance, associations of TLR diversity with fitness-related traits have rarely been examined in wild animal populations. Here, we tested for associations of TLR polymorphism with physiological condition in a colonial waterbird, the Black-headed Gull (Chroicocephalus ridibundus). Physiological condition and polymorphism at 4 TLR loci were assessed in 60 gulls from a breeding colony in northern Poland. We found that blood hemoglobin and plasma albumin concentrations were positively associated with TLR diversity across all genotyped loci. Plasma concentrations of albumin and triglycerides were also associated with the presence of specific TLR variants and locus-specific diversity. All significant associations between physiological condition and TLRs were primarily apparent at the level of nucleotide, rather than amino acid allelic variants. Although the exact molecular mechanisms responsible for these associations require further investigation, our study provides strong correlational support for links between TLR diversity and physiological condition in a wild avian population, and it adds to the growing, but still modest, body of evidence for the fitness-related consequences of individual TLR repertoire in wild birds.