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The non‐breeding season presents significant energetic challenges to birds that breed in temperate or polar regions, with clear implications for population dynamics. In seabirds, the environmental conditions at non‐breeding sites drive food availability and the energetic cost of regulatory processes, resulting in variation in diet, behaviour and energetics; however, very few studies have attempted to understand if and how these aspects vary between populations. We investigated whether non‐breeding location influenced diet, behaviour and energetics in the common guillemot Uria aalge. We studied guillemots from four UK breeding colonies, two located on the west coast of Scotland and two on the east. We quantified non‐breeding distribution, foraging behaviour and activity budgets of 39 individuals from July to March, using geolocation–immersion loggers and time‐depth recorders, and used feather stable isotope signatures to infer diet during the post‐breeding moult. We calculated energy expenditure and investigated whether the peak (an indicator of the potential vulnerability to marine threats) varied between colonies. Individuals were spatially segregated according to the coastline they breed on, with west coast guillemots distributed off the west coast of the UK and east coast guillemots distributed off the east coast. Diet and behaviour were more similar in guillemots that shared a breeding coastline than those that did not, as west coast guillemots foraged at a lower trophic level, spent less time diving and engaged in more pelagic foraging than east coast guillemots. However, energy expenditure was remarkably similar between colonies, peaking during late February/early March, indicating that, during our study period, there was high synchrony between colonies in the timing of potential vulnerability to marine threats. Therefore, any anthropogenic changes that result in decreased food availability or increased energy expenditure during late winter may have greater impacts on energy balance, with consequences for population dynamics. [ABSTRACT FROM AUTHOR]

Highlights: [•] We identified key foraging areas of breeding European shags over a 23-year period. [•] 8years’ data captured over 90% of the foraging area used during the study period. [•] Over 60% of this area was captured with just 2years’ data. [•] Foraging range varied with sex, environmental conditions and population density. [•] Foraging locations of birds from different sub-colonies were spatially segregated. [Copyright &y& Elsevier]

Relationships between events in one period of the annual cycle and behaviour in subsequent seasons are key determinants of individual life histories and population dynamics. However, studying such associations is challenging, given the difficulties in following individuals across seasons, particularly in migratory species. Relationships between breeding performance and subsequent winter ecology are particularly poorly understood, yet are likely to be profoundly important because of the costs of reproduction. Using geolocation technology, we show that black-legged kittiwakes that experienced breeding failure left their colony in southeast Scotland earlier than successful breeders. Moreover, a greater proportion of unsuccessful breeders (94% versus 53% successful) travelled over 3000 km to the West Atlantic, whereas fewer visited the East Atlantic (31% versus 80% successful), less than 1000 km from the colony. The two groups did not differ in the timing of return to the colony the following spring. However, 58 per cent of males made a previously undescribed long-distance pre-breeding movement to the central Atlantic. Our results demonstrate important links between reproductive performance and winter distribution, with significant implications for population dynamics. Furthermore, macro-scale segregation associated with breeding outcome is relevant to defining important wintering areas, in particular among declining species experiencing increasingly regular breeding failure. [ABSTRACT FROM AUTHOR]

Determining the precise timing and location of major demographic bottlenecks, such as periods of low survival, is key to identifying ecological causes of variation in population growth rate. Such understanding is key to designing efficient and effective mitigation. In a protected population of red-billed chough Pyrrhocorax pyrrhocorax on Islay, Scotland, variation in population growth rate largely reflects among-year variation in first-year survival. First-year survival was unprecedentedly low during 2007-2010, threatening population viability. We used colour-ring resightings to estimate monthly survival probabilities (Φ) throughout the first year from fledging for eight chough cohorts (totalling 519 individuals) representing the full observed range of variation in first-year survival. We thereby identify the time and location of recent low survival. On average across all cohorts, Φ varied among months, being low during the first month after ringing (May-June, accounting for c. 24% of all first-year mortality) and high during the last 4 months of the first year (January-May, accounting for c. 6% of all first-year mortality). Most mortality ( c. 70%) occurred after fledglings dispersed from natal territories. The 2007-2009 cohorts experienced low Φ during July-December. This represents an additional low survival period compared to previous cohorts rather than decreased Φ across all months or further decreases through periods when Φ was low across all cohorts. Synthesis and applications. These data have general relevance in showing that dramatically low annual survival, which needs to spark rapid management action, can reflect different and unanticipated periods of low survival rather than exaggeration of typical variation. With specific regard to conserving Islay's chough population, our data show that sub-adult survival has recently been low during July-December, probably reflecting conditions on key grassland foraging areas. Managers aiming to increase population viability should increase invertebrate diversity, abundance and availability at these times and locations, thereby increasing foraging options available to choughs. [ABSTRACT FROM AUTHOR]