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Seabirds are compelled to nest on land, away from their feeding areas, which they can only reach by leaving eggs or chicks in the nest, often for long periods of time. For this reason, almost all of them have evolved social monogamy as a reproductive system, cooperation between partners for incubation and chick rearing, and long-lasting pair bonds. Additionally, nesting conditions are essential for successful reproduction, and the nest can be considered a resource if it provides more guarantees in this aspect. As a result, the nest may be a source of contention and intraspecific competition, especially among males. In this work, we analyze long-term data of the Scopoli's shearwater (Calonectris diomedea) population to address the fitness consequences of nest change regarding survival and reproductive success. We used capture–recapture multistate models and the AICc model selection approach to test three hypotheses: breeding failure triggers nest change; nest change affects breeding success probability; nest change affects survival. Each year, about 5% of the breeders move to a new nest. For males, it was mainly a way to improve their breeding conditions and was observed in their early years as a breeder. Conversely, for females, it was a way to improve their reproductive performance by trying with a new mate after a failure. Males that changed nests improved their breeding success probability. Instead, in females, there was no causal relation between nest change and breeding success, the latter having been more influenced by the intrinsic quality of the female as a breeder. We did not even find a link between nest change and survival. Instead, we demonstrated that reproductive failure could affect the apparent survival of females, probably because it induces breeding dispersal. [ABSTRACT FROM AUTHOR]

The ecological drivers underlying breeding performance are expected to differ across the geographical range of seabird species, but few studies have compared trade-offs between colonies with different local conditions. During chick-rearing (2000–01), we compared the foraging trips, diet and breeding parameters of two Adélie penguin colonies in the Ross Sea, at Edmonson Point (EdPo; ~2000 breeding pairs) and Inexpressible Island (InIs; ~24 000 breeding pairs). Penguins from InIs travelled farther and performed longer feeding trips. The quantity of food brought to the nest was the same for the two colonies, but penguins from InIs brought more fish and less krill. Eggs hatched earlier at EdPo. Breeding success did not differ, but chick weight during hatching–fledging was greater at InIs. Despite worse weather conditions at InIs, the larger proportion of high-energy food brought by penguins from InIs (i.e. fish) may explain their offspring's better performance. In addition, the persistence of fast ice at EdPo may have led to greater energy expenditure of breeding individuals, possibly reducing chick growth. The greater intraspecific competition expected at InIs may have been reduced by longer foraging trips and/or counteracted by the more nutritious diet. Our findings reveal complex trade-offs between foraging effort and environmental constraints in determining the breeding performance of Adélie penguins. [ABSTRACT FROM AUTHOR]

When selecting a breeding site, individuals can use social information to reduce the uncertainty regarding habitat quality. Individuals of several bird species tend to reuse nests previously occupied by conspecific or heterospecific competitors but the proximate mechanisms underlying this behaviour remain unclear. Reoccupying nests previously used by competitors could result from individuals copying competitors' choices (the 'social information' hypothesis). Alternatively, it could allow individuals to fulfil their need for a soft nest substrate (e.g. by improving thermal insulation or reducing egg breakage risks) at low costs, regardless of previous occupancy (the 'comfort' hypothesis). Here, we aimed to determine which of these nonmutually exclusive mechanisms triggered the preference for old conspecific nest material in a secondary cavity-nesting raptor that does not add lining material to its nests, the lesser kestrel, Falco naumanni. Using an experimental design forcing settling lesser kestrels to choose between two adjacent nestboxes containing different substrates, we detected a strong preference for soft substrates (peat moss or old conspecific or European roller, Coracias garrulus , nest material) over coarse mineral substrate, especially when the soft substrate also provided social information about previous nest use by a competitor. Despite the apparent absence of preference when directly comparing settlement patterns in soft substrates with and without social information, early settling individuals favoured the substrate with social information, while late settling ones favoured the substrate without social information. This could reflect intraspecific competition avoidance by late arriving individuals that may be competitively inferior to early arriving ones. This hypothesis is supported by a later laying date of young breeders in our population. Our findings suggest that both comfort seeking and social information use explain the preference for previously used nest cavities, and that nest site choices may depend on individual competitive abilities and experience. • The proximate mechanisms underlying the reuse of old nest material are diverse. • Lesser kestrels preferred soft nest substrates, with or without social cues. • Between two soft substrates, early breeders favoured the one providing social cues. • Late breeders, mostly young, preferred soft substrates with no social cues. • Lesser kestrels may adjust social information use according to individual traits. [ABSTRACT FROM AUTHOR]