Inter-colony foraging dynamics and breeding success relate to prey availability in a pursuit-diving seabird

Abstract

Spatial patterns of breeding seabirds are influenced by the distribution of resources in relation to the colony and the density of conspecifics from the same or adjacent colonies. We conducted an inter-colony comparison of foraging space use and behavior, diet, and reproductive success of common murres Uria aalge breeding at a large offshore and a small inshore colony on the northeastern coast of Newfoundland (Canada) during 2016-2018 under varying prey (capelin Mallotus villosus) biomass. Murres from the large offshore colony foraged over a greater area, with greater individual foraging distances, indicative of higher commuting costs compared to the smaller inshore colony. Although this pattern might reflect prey depletion near the offshore colony due to higher conspecific densities, it likely also reflects the greater distance to predictable, high-abundance prey aggregations. This is supported by high spatial overlap of foraging areas from both colonies near coastal, annually persistent capelin spawning sites. Adult diet was similar between colonies during incubation, but diverged during chick-rearing, with offshore murres consuming a higher proportion of alternative prey, while inshore murres consumed more capelin. These differences did not affect fledging success, although hatching success was lower in the larger colony, suggesting that divergent factors (e.g. predation, nest attendance) influence colony-specific population dynamics. Overall, our findings suggest that abundant local prey is key in shaping spatial patterns of breeding common murres in northeastern Newfoundland and results in apparently minimal intraspecific competition. As anthropogenic pressures on resource availability heighten, insight into factors influencing intraspecific foraging niche dynamics will be critical to inform management.

Local prey shortages drive foraging costs and breeding success in a declining seabird, the Atlantic puffin

“…The link between fish availability and breeding success is well known in seabirds, including puffins (Cury et al., 2011; Durant et al., 2003). However, the low breeding success we observed is not simply caused by a general decrease in prey abundance near breeding grounds, which could lead to a switch to alternative prey without affecting foraging distance, as observed in other auks (Gulka et al., 2020; Ito et al., 2009). Instead, our results indicate that it is due to a combination of low prey availability near the colony, forcing birds to feed further, and a lack of suitable prey within the extended foraging range, as evidenced by birds’ higher foraging effort on longer trips, prey load composition in northern colonies (two to three times more and smaller items than in Wales), and by our diet analyses.…”

“…These increased breeding costs can have negative carry‐over effects on future breeding performance (Fayet, Freeman, Shoji, Kirk, et al., 2016), increase the likelihood to skip breeding (Shoji, Aris‐Brosou, et al., 2015) or lead parents to prioritise survival and abandon breeding (Erikstad et al., 2009; Wernham & Bryant, 1998). However, other studies have shown that despite having to forage further in certain conditions, auks can maintain breeding success through behavioural plasticity (Gulka et al., 2020) even while maintaining condition (Grémillet et al., 2012). Therefore, the lower breeding success associated with longer feeding distances in our study suggests that the efforts required to maintain chick‐provisioning under the conditions near some colonies exceeded the puffins’ ability or willingness to adjust their foraging behaviour.…”

Potential climate-driven changes to seabird demography: implications for assessments of marine renewable energy development

“…This limitation would be further constrained by heterogeneity in other habitat features, such as those affecting prey habitat suitability, as well as anthropogenic pressures such as fisheries activity. Moreover, there is emerging evidence that larger foraging distances may impose constraints on chick condition and subsequent breeding success, highlighting potentially important trade-offs between wider access to resources and subsequent fitness (Horswill et al 2017, Campbell et al 2019, Gulka et al 2020.…”

Geographic, ecological, and temporal patterns of seabird mortality during the 2022 HPAI H5N1 outbreak on the island of Newfoundland

“…In contrast, Northern Gannets have a much larger foraging range than Atlantic Puffins, Black-legged Kittiwakes, and Common Murres (d 'Entremont et al 2022), so are less likely to overlap at sea with allospecifics from the same colony, but forage and raft with conspecifics at foraging hotspots (e.g., Carter et al 2016;d'Entremont et al 2022). All four species feed on capelin when it is available early in the breeding season (Hatch et al 2020;Lowther et al 2020;Ainley et al 2021;d'Entremont et al 2022), so allospecific interaction at sea with individuals from the same colony is likely during this time. When capelin complete spawning, gannets forage farther away from the breeding colony for larger fish like mackerel (d 'Entremont et al 2022), and thus are less likely to share foraging areas with the smaller seabirds later in the breeding season.…”

“…As AIV transmission generally requires close contact between individuals or contact with contaminated environments (Ramey et al 2020), we expect that species which frequently come into contact with con-and allospecifics at the colony or at sea are more likely to contract and spread the virus. Interindividual contact is likely for species that (1) nest in high densities (e.g., Black-legged Kittiwakes;Hatch et al 2020;Lowther et al 2020;Ainley et al 2021;Careen et al Accepted). We also hypothesize that interindividual contact is likely for species that (5) scavenge or feed on other birds (e.g., Larus spp.)…”