Effect of breeding performance on the distribution and activity budgets of a predominantly resident population of black-browed albatrosses

Abstract

Pelagic seabirds breeding at high latitudes generally split their annual cycle between reproduction, migration, and wintering. During the breeding season, they are constrained in their foraging range due to reproduction while during winter months, and they often undertake long-distance migrations. Black-browed albatrosses (Thalassarche melanophris) nesting in the Falkland archipelago remain within 700 km from their breeding colonies all year-round and can therefore be considered as resident. Accordingly, at-sea activity patterns are expected to be adjusted to the absence of migration. Likewise, breeding performance is expected to affect foraging, flying, and floating activities, as failed individuals are relieved from reproduction earlier than successful ones. Using geolocators coupled with a saltwater immersion sensor, we detailed the spatial distribution and temporal dynamics of at-sea activity budgets of successful and failed breeding black-browed albatrosses nesting in New Island, Falklands archipelago, over the breeding and subsequent nonbreeding season. The 90% monthly kernel distribution of failed and successful breeders suggested no spatial segregation. Both groups followed the same dynamics of foraging effort both during daylight and darkness all year, except during chick-rearing, when successful breeders foraged more intensively. Failed and successful breeders started decreasing flying activities during daylight at the same time, 2-3 weeks after hatching period, but failed breeders reached their maximum floating activity during late chick-rearing, 2 months before successful breeders. Moon cycle had a significant effect on activity budgets during darkness, with individuals generally more active during full moon. Our results highlight that successful breeders buffer potential reproductive costs during the nonbreeding season, and this provides a better understanding of how individuals adjust their spatial distribution and activity budgets according to their breeding performance in absence of migration.

Keywords: active foraging; breeding failure; carry‐over effects; migration; reproductive cost; sustained flight; wintering grounds.

Figure 1

Raw activity data of dry events for successful (blue) and failed (red) black‐browed albatrosses. Dry events longer than the threshold duration of 16 hr (dashed horizontal line) were considered as periods on land, since they occurred only during the breeding season. Gray areas represent the different phases of breeding, from hatching (H) to brooding (B) and chick‐rearing period (C)

Figure 2

Monthly spatial distribution of successful (blue) and failed (red) breeding black‐browed albatrosses represented by 50% and 90% UD contours. The star represents the breeding colony of New Island. Note that distributions for March and September are only based on data from the first 10 days, as locations around equinoxes are unreliable

Figure 3

Temporal dynamics of the proportion of time spent foraging, flying, and floating on the water over the annual cycle of failed (red) and successful breeders (blue) during daylight (upper panel) and darkness periods (lower panel). Colored shaded areas represent 95% confidence intervals while dark to light gray areas represent hatching, chick brooding, and chick‐rearing period

Figure 4

Mean ± SD percentage of time spent foraging, floating, and flying for (a) daylight and (b) darkness according breeding performance, sex, and annual cycle (chick‐rearing: 28/01/2012 to 25/02/2013; nonbreeding: 24/06/2013 to 21/07/2013)

Figure 5

Effect of the moon cycle on the proportion of time spent foraging, flying, and floating on the water during daylight (upper panel) and darkness periods (lower panel), regardless of individual breeding performance. Day 1 corresponds to new moon while day 15 corresponds to full moon. Shaded areas represent 95% confidence intervals