Effects of environmental variability and offspring growth on the movement ecology of breeding Scopoli’s shearwater Calonectris diomedea

Abstract

Most seabird species display colonial behavior during the breeding period which implies that food resources around breeding sites can easily go depleted. Seabirds need to both reach profitable areas, which can be located far from the colony, and return to the colony regularly. In this context, flexibility in movement behavior may be crucial for breeding success. During chick-rearing, Procellariformes species can alternate short trips lasting 1–4 days for chick provisioning with longer trips for self-provisioning in what has been called a dual-foraging strategy. We analyzed foraging trips from 136 Scopoli’s shearwaters from three Mediterranean colonies tracked with GPS during 6 chick-rearing seasons to assess whether the adoption of a dual foraging strategy depends on the quality of habitat surrounding the colony. We found a marked dual-foraging strategy only in birds from the Linosa colony which was the largest colony in terms of breeding pairs and was characterized by having a lower marine habitat quality. Birds from this colony performed foraging trips that extended up to 369 km from the nest and lasted more than 10 days. In general, the decision to perform long lasting trips was triggered by lower values of primary production and higher offspring weight. Contrary to expectation, the decision to feed far from the colony was not related to the parents’ weight. At the same time, despite the higher productivity offered by distant areas, the higher proportion of long trips performed by birds breeding in poor areas was not sufficient to maintain the same body mass as the ones breeding in richer areas.

The Effect of Moonlight on Scopoli's Shearwater Calonectris diomedea Colony Attendance Patterns and Nocturnal Foraging: A Test of the Foraging Efficiency Hypothesis

“…During chick rearing, foraging trips of adults last from one to several days (Cecere et al. , ), and birds were handled during the night. As adults normally spent little time in their burrow, it was not always possible to recapture the equipped bird after the first foraging trip, and hence, more than one trip might have been recorded for a given bird.…”

A new algorithm for the identification of dives reveals the foraging ecology of a shallow-diving seabird using accelerometer data

“…During short trips, Scopoli's shearwaters from Linosa have only access to low productive foraging areas surrounding the colony (Cecere et al 2014) due to the need to feed the chick frequently. Therefore, parents increased their foraging effort at the beginning of chick-rearing to maximise the energy delivery to the chick in time constraint conditions, in accordance with the model proposed by Ydenberg et al (1994).…”

“…This dual-foraging strategy occurs especially in colonies surrounded by low productive waters (Granadeiro et al 1998;Paiva et al 2010a). Thus, under these conditions, short trips for chick-feeding occur in sub-optimal foraging areas close to the colony (Paiva et al 2010b;Cecere et al 2014) at the expense of the parental body condition (Weimerskirch et al 1994). Conversely, long trips allow birds to visit more profitable areas far away from the colony to feed for themselves and replenish their energy reserves (Baduini and Hyrenbach 2003;Magalhães et al 2008).…”

“…Conversely, long trips allow birds to visit more profitable areas far away from the colony to feed for themselves and replenish their energy reserves (Baduini and Hyrenbach 2003;Magalhães et al 2008). The Scopoli's shearwaters nesting in Linosa Island are surrounded by low productive waters which are exploited by birds during short foraging trips (Cecere et al 2014). Thus, we expected an increase of foraging effort performed by birds (i.e., high dive rates) during short trips compared with long trips.…”

Commercial fisheries, inter‐colony competition and sea depth affect foraging location of breeding Scopoli's Shearwaters Calonectris diomedea

“…) during the breeding period, particularly when the waters surrounding the colony are characterized by a lower quality (Cecere et al . ). The behavioural plasticity of the species is also supported by the evidence that Scopoli's Shearwaters can adopt different movement strategies in relation to different biological constraints.…”