Asian koel rapidly locates host breeding in novel nest sites.

Avian brood parasites depend upon locating host nests to lay their eggs. However, how brood parasites locate host nests and select the nests for parasitism remains poorly studied. Here, we examined how a non-evicting brood parasite, the Asian koel (Eudynamys scolopaceus) were able to locate host nests in locally novel nest sites. We provided a set of novel nest sites (i.e., nestboxes, n = 100) to the common myna (Acridotheres tristis), a regular host of the Asian koel, at a field site in Central Bangladesh. We found that common myna quickly utilized the novel breeding sites (n = 99 nests across 59 boxes) and similarly, 21.2% of these nests were parasitized by the Asian koel. Unsurprisingly, none of the inactive nest boxes were parasitized, neither were empty nests of common myna (i.e., either predated or fledged clutches, thus lack of parental activity, n = 83). Our results provide an experimental demonstration of the Asian koel ability to rapidly locate nests in locally novel nest sites, potentially facilitated by close monitoring of host activity and behavior around the nest site. However, the underlying mechanisms for this rapid adjustment to novel nest sites remain unresolved.

Face masks in action: Birds show reduced fear responses to people wearing face masks during the COVID-19 pandemic in three Asian countries.

The 2019 zoonotic pandemic (COVID-19), has led to a massive global lockdown that provides a good opportunity to study how wildlife responds to changes in human activity. Wearing a mask after the COVID-19 outbreak was widely used to prevent the spread of the causative pathogen. It has been shown that tree sparrows (Passer montanus) at two sites in south China exhibit reduced fear responses to people with face masks after a period of heavy exposure to them, whereas European studies showed the opposite, with no changes in the behaviour of the birds towards mask wearers in either rural or urban areas. To further study this, from October 2021 to January 2022, we conducted a flight initiation distance (FID) survey in Pakistan, Bangladesh, and Xi'an, China for a variety of field bird species by comparing the FID for researchers wearing masks to that for researchers not wearing masks to assess whether wearing masks in public places caused birds to adjust their flight response. Results from the three Asian countries showed that after a period of sustained contact with people wearing masks, in both rural and urban areas, birds were significantly more adapted to them and had a shorter FID to people wearing masks. We suggest that the rapid habituation of birds to people wearing masks with a reduced fear response could have some fitness advantage, allowing them to adapt rapidly to the new environmental conditions induced by COVID-19.

No evidence of host-specific egg mimicry in Asian koels.

Avian brood parasitism is costly for the host, in many cases leading to the evolution of defenses like discrimination of parasitic eggs. The parasite, in turn, may evolve mimetic eggs as a counter-adaptation to host egg rejection. Some generalist parasites have evolved host-specific races (gentes) that may mimic the eggs of their main hosts, while others have evolved 'jack-of-all-trades' egg phenotypes that mimic key features of the eggs of several different host species. The Asian koel (Eudynamys scolopaceus) is a widely distributed generalist brood parasite that exploits a wide range of host species. Based on human vision, previous studies have described Asian koel eggs as resembling those of its main host, the house crow (Corvus splendens). Using measurements of egg length and breadth, digital image analysis, reflectance spectrophotometry and avian visual modelling, we examined Asian koel egg variation and potential mimicry in egg size and shape, and eggshell pattern and color in three sympatrically occurring host species in Bangladesh: the common myna (Acridotheres tristis), house crow, and long-tailed shrike (Lanius schach). We found some differences among Asian koel eggs laid in different host nests: a) Asian koel eggs in long-tailed shrike nests were larger than those laid in common myna and house crow nests, and b) Asian koel eggs in house crow nests were less elongated than those in common myna nests. However, these changes in Asian koel egg volume and shape were in the opposite direction with respect to their corresponding host egg characteristics. Thus, our study found no evidence for Asian koel host-specific egg mimicry in three sympatrically occurring host species.