Unconditional adoption rules out the need for parent–offspring recognition in a single‐brooded colonial seabird

Parent–offspring recognition (POR) is fundamental in colonial birds when the potential intermingling of chicks is higher due to the large number and proximity of nests. In species with isolated nests, where chick presence in the nest is strong contextual evidence of kinship, there might be circumstances when the parent might doubt the identity of the chick, but not enough to reject it. Olfactory-based recognition of conspecifics and nest sites in birds has gained strong evidence suggesting a potential role of olfaction in POR. Despite that, there are no studies testing it. We used Scopoli's shearwater (Calonectris diomedea) as model colonial single-brooded species with a developed olfactory sense, usually breeding in well-spaced nests with low probability of chicks mixing. We tested the parent's ability to selectively respond to their own chick as opposed to a simpler rule of feeding any chick found in the nest by means of chick-fostering experiments. We designed two cross-fostering experiments using chicks of different ages to test whether the ability of parents to recognize a related chick develops over time, possibly after acquiring an own distinctive odour. Finally, we also manipulated nests’ odour to disentangle the confounding effect of nest site recognition from POR when parents return at night. All experimental chicks were adopted by parents as the weight and bill growth of cross-fostered chicks did not differ significantly from the control group. We recorded a small difference in weight when foster chicks were inside an odour-manipulated nest; although we did not record weight loss in experimental chicks, only a steeper increase in weight was observed in control chicks. In conclusion, adoption in Scopoli's shearwater seems to follow the rule "if the young is in my nest, accept it" proposed by Beecher (1991) for species with spatially separated nests and low chick mobility.Fundação para a Ciência e Tecnologia - FCTinfo:eu-repo/semantics/acceptedVersio

Patterns of GPS Tracks Suggest Nocturnal Foraging by Incubating Peruvian Pelicans (Pelecanus thagus)

Most seabirds are diurnal foragers, but some species may also feed at night. In Peruvian pelicans (Pelecanus thagus), the evidence for nocturnal foraging is sparse and anecdotal. We used GPS-dataloggers on five incubating Peruvian pelicans from Isla Lobos de Tierra, Perú, to examine their nocturnality, foraging movements and activities patterns at sea. All instrumented pelicans undertook nocturnal trips during a 5–7 day tracking period. Eighty-seven percent of these trips (n = 13) were strictly nocturnal, whereas the remaining occurred during the day and night. Most birds departed from the island after sunset and returned a few hours after sunrise. Birds traveled south of the island for single-day trips at a maximum range of 82.8 km. Overall, 22% of the tracking period was spent at sea, whereas the remaining time was spent on the island. In the intermediate section of the trip (between inbound and outbound commutes), birds spent 77% of the trip time in floating bouts interspersed by short flying bouts, the former being on average three times longer than the latter. Taken together, the high sinuosity of the bird's tracks during floating bouts, the exclusively nocturnal trips of most individuals, and the fact that all birds returned to the island within a few hours after sunrise suggest that pelicans were actively feeding at night. The nocturnal foraging strategy of Peruvian pelicans may reduce food competition with the sympatric and strictly diurnal Guanay cormorants (Phalacrocorax bougainvillii), Peruvian boobies (Sula variegata) and Blue-footed boobies (S. nebouxii), which were present on the island in large numbers. Likewise, plankton bioluminescence might be used by pelicans as indirect cues to locate anchovies during their upward migration at night. The foraging success of pelicans at night may be enhanced by seizing prey close to the sea surface using a sit-and-wait strategy

Groping in the Fog: Soaring Migrants Exhibit Wider Scatter in Flight Directions and Respond Differently to Wind Under Low Visibility Conditions

Atmospheric conditions are known to affect flight propensity, behaviour during flight, and migration route in birds. Yet, the effects of fog have only rarely been studied although they could disrupt orientation and hamper flight. Fog could limit the visibility of migrating birds such that they might not be able to detect landmarks that guide them during their journey. Soaring migrants modulate their flight speed and direction in relation to the wind vector to optimise the cost of transport. Consequently, landmark-based orientation, as well as adjustments of flight speed and direction in relation to wind conditions, could be jeopardised when flying in fog. Using a radar system operated in a migration bottleneck (Strait of Messina, Italy), we studied the behaviour of soaring birds under variable wind and fog conditions over two consecutive springs (2016 and 2017), discovering that migrating birds exhibited a wider scatter of flight directions and responded differently to wind under fog conditions. Birds flying through fog deviated more from the mean migration direction and increased their speed with increasing crosswinds. In addition, airspeed and groundspeed increased in the direction of the crosswind, causing the individuals to drift laterally. Our findings represent the first quantitative empirical evidence of flight behaviour changes when birds migrate through fog and explain why low visibility conditions could risk their migration journey

Citizen science data reveal possible multi-decadal phenological changes in the arrival time of a migratory tropical seabird species at the breeding ground

· Changes in climate and weather variability are having global impacts on the lives of organisms, particularly on upper trophic-level predators such as pelagic seabirds. In the North Atlantic, migratory seabirds are expected to respond to climate variability by adjusting their seasonal events, including the timing of migration and arrival at the breeding site. The timing of these events may be infuenced by large-scale atmospheric phenomena such as the North Atlantic Oscillation (NAO) and the Atlantic Multi-decadal Oscillation (AMO) that gauge temporal and spatial variation in environmental conditions across the North Atlantic. In the Bermuda Islands (32° 17′ 58″ N, 64° 47′ 25″ W), the White-tailed tropicbird (Phaethon lepturus catsbyii) is one of the few breeding seabird species which returns every year between February and March after migration. According to local belief their return announces the arrival of Spring, and this cultural importance means that the event is noticed. Only recently, early tropicbird returns have been recorded and associated with unusual climate/weather conditions experienced across the region. This raised the question of whether the species is showing some change in its phenology and whether it might be afected by changing climatic conditions. To answer this question, we investigated tropicbird arrival dates at Bermuda using current and historic observation data retrieved from the eBird citizen science platform. After accounting for biases inherent to opportunistic data collection, we selected and used the frst annual observation as a proxy for bird arrival time at the Bermuda breeding ground from 1953 to 2023. We found that tropicbird observation dates advanced substantially over the past 70 years suggesting that arrival time has been likely shifting of ca. 20–25 days. However, frst observation dates were not related to the variation in annual or winter NAO and AMO Indices, and further investigation is required to understand the underlying causes of these progressively early arrivals. Overall, the study highlights that citizen-science data can be used to unveil hidden phonological patterns when a standardized long-term data collection is missing.Fundação para a Ciência e Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio

Immunohistochemical localisation and molecular expression of the steroidogenic enzyme cytochrome P450 17α-hydroxylase ⁄C(17,20)-lyase in the vestibular nuclei of adult male rats

Many biologically active neurosteroids, including dehydroepiandrosterone (DHEA), are synthesised in the brain. DHEA is a potent endogenous modulator of several neuronal functions, and alterations of DHEA are correlated with various neurobiological deficits. The cytochrome P450 17α-hydroxylase ⁄ C(17,20)-lyase (P450C17) plays a pivotal role in the synthesis of DHEA from pregnenolone and progesterone. We investigated the immunohistochemical localisation and molecular expression of P450C17 in the superior, lateral, medial and inferior vestibular nuclei (VCN) of adult male rats by western blotting and indirect immunofluorescence analysis. Immunoreactive P450C17 was widely distributed in all VCN and the expression of P450C17 was confirmed by western blot analysis. The present study demonstrates, for the first time, the presence and anatomical distribution of P450C17 in the VCN. Given that neurosteroids can modulate neuronal activities in the medial vestibular nucleus, DHEA synthesised in the VCN may play an important role in the control of specific activities at this level

Cytochrome P450 17α-hydroxylase/C(17,20)-lyase immunoreactivity and molecular expression in the cerebellar nuclei of adult male rats

Several probes have been developed to identify steroidogenic activity in the brain of vertebrates. However, the presence of the cytochrome P450 17α-hydroxylase/C(17,20)-lyase (P450C17), an enzyme that converts pregnenolone and progesterone into dehydroepiandrosterone and androstenedione, in specific areas of the cerebellum such as the deep cerebellar nuclei, remains virtually unexplored. Using Western blot analysis and immunohistochemistry, we found molecular expression of P450C17 in the lateral, interposed and medial deep cerebellar nuclei. Moreover, double immunofluorescence procedures enabled localization of P450C17 mainly in neurons, axons and glutamatergic synapses. Taken together, these data demonstrate the occurrence of P450C17 in the deep cerebellar nuclei, and enable the chemical characterization of the cells that express the cytochrome