Protandrous migration and variation in morphological characters in Emberiza buntings at an East Asian stopover site

Abstract

The effect of the timing of spring migration on reproductive success differs between the sexes. As a consequence, various sex‐specific tactics relating to the timing of migration have evolved in migratory avian groups. Various hypotheses have been proposed to explain differential migration to breeding or wintering grounds, and inter‐ and intrasexual size differences are often considered one of the proximate mechanisms. We investigated arrival patterns in the spring by individuals of each sex, sexual size dimorphism and related morphological variables, and the relationship between size variation and arrival date in five bunting species that passed through an East Asian migratory flyway stopover site in 2006–08. Males of all the study species arrived before females, and significant sexual dimorphism was observed. Several morphological characters, including total length, wing‐length and tail‐length, contributed to the size variation. Although larger males arrived earlier, there was no relationship between arrival date and size in females. Our study confirmed that East Asian buntings display a discriminated protandrous migration pattern at the stopover site as well as at the breeding grounds. This is consistent with the view that larger body size in males is favoured due to its association with early arrival to help ensure access to the best resources and hence enhanced mating success.

Migratory songbirds in the East Asian-Australasian Flyway: a review from a conservation perspective

“…In northern China, Wang et al (2006b) sampled Orange-flanked Bush-robin Tarsiger cyanurus at a stop-over site in Heilongjiang and was able to document gains in mass by birds on passage, as well as evidence of differential arrival timings of males and females, a pattern that might indicate temporal partitioning to reduce competition. Age or sex-related temporal partitioning within species as shown in Wang et al (2006b) in China and in Nam et al (2011) in Korea, or between ecologically similar species can minimise competition during stop-over, but may also result from differential latitudes of the breeding ranges, as suggested in Imanishi et al (2009) which studied autumn migration timings of three Phylloscopus warblers in Japan.…”

“…Many of these survey sites are likely to involve small islands or continental sites containing known concentrations of migratory songbirds (Table 6, Figure 1), which can be sampled by a combination of judicious bird banding (e.g. Ozaki 2008, Nam et al 2011) and visual surveys of abundance using points or transects (e.g. Moores 2012).…”

“…Although detailed life history studies of some species in their breeding ranges in East Asia exist (e.g. Wang et al 2006a, Imanishi et al 2009, Gluschenko et al 2011), the migration connectivity, strategies, wintering distributions and ecology of many long-distance passerine migrants in the East Asian migration system remain poorly understood (Greenberg and Marra 2005, Nam et al 2011, Moores 2012). This is despite their ecological significance in both temperate and tropical biomes, given their abundance and roles in trophic (e.g.…”

Migration phenology determines niche use of East Asian buntings (Emberizidae) during stopover

“…2016 ). The occurrence of the so-called protandrous migration in East Asian buntings was shown by Nam et al. (2011) at a stopover site on the Korean Peninsula, and was also found in Ortolan Bunting E. hortulana along the west end of the Asian continent ( Yosef and Tryjanowski 2002 ).…”

“…East Asian buntings show sexual size dimorphism, with males being bigger, longer winged and longer tailed ( Nam et al. 2011 ).…”