Many seabird species share characteristics of high inter-annual colony fidelity and prolonged mate fidelity. This study investigates these characteristics in a Sooty Tern Onychoprion fuscatus breeding colony. During the 2021 breeding season, both members of 80 pairs of incubating Sooty Terns were individually ringed in a large breeding colony on Bird Island, Seychelles. Ten pairs were ringed in each of eight identifiable locations within the nesting area. In the 2022 and 2023 breeding seasons, ringed birds were searched for throughout the colony and caught for identification. Their nest sites were marked and their mates were subsequently caught, then identified or ringed. In the two years of study, many birds retained approximate nests sites between years; when birds did change, alterations in colony vegetation could have been responsible. The extent of nest site change between years was likely underestimated, however, due to reduced search effort available in 2023. Between year mate changes suggested that many Bird Island Sooty Terns did not maintain long-term pair bonds and the causes and implications of this are discussed.

Although treecreepers Certhia spp. are known to roost communally, the factors associated with roost use have never been quantified. Here, we investigate the influence of environmental conditions on the roosting behaviour of Short-toed Treecreepers C. brachydactyla in an urban setting in The Netherlands. We performed transect-based nocturnal counts of 120 roosts on 487 days during a three-year period. We correlated total number of birds per roost per day to multiple relevant environmental factors (daily duration of precipitation, daily sum of precipitation, daily mean wind direction, daily mean wind speed, daily maximum temperature, daily minimum temperature, daily mean temperature, daily mean humidity and daylength). Numbers of roosting Treecreepers were positively associated with minimum daily temperature and northern winds and negatively with day length and maximum daily temperature. Our study shows that Treecreepers respond to short-term temperature fluctuations by altering their roosting strategy. Communal roosting in the species is thus likely a behavioural response to a combination of severe weather and short day length. Most roosts are generally vacant (86.8 ± 3.5% SD) or hold single roosting treecreepers (7.6 ± 3.9%) and a few apparently optimal sites hold consistently large numbers (6.6 ± 3.5%). Vacant roosts peak in number during the breeding season (89.5 ± 3.8% vs. 85.8 ± 2.9% in winter), whereas singleton roosts (8.0 ± 4.2% vs. 6.7 ± 2.5% in the breeding season) and communal roosts (7.3 ± 3.4% vs. 4.8 ± 3.3% in the breeding season) are most common during winter. Our study fills an important gap in our knowledge of roosting behaviour in passerine birds, but much remains to be learned.

‘Ino’ colouration is a remarkably rare plumage colour aberration characterized by a significant qualitative reduction in melanin and reddish eyes. Here we describe the first report of ino colouration in a wild passerine bird species, the European Pied Flycatcher Ficedula hypoleuca. We found a nestling with an ino colouration aberration distinguishable from its siblings by its red eyes and the absence of pigmented feathers on the forelimbs at hatching. At the fledging age, the ino individual presented with reddish eyes and pale brown feathers and bill. All the chicks successfully fledged at the end of the nestling period. The most plausible hypothesis that explains this finding is a genetic mutation that affects the deposition of melanin pigments in feathers.