Spatial ecology, phenological variability and moulting patterns of the Endangered Atlantic petrel Pterodroma incerta

Abstract

Insights into the year-round movements and behaviour of seabirds are essential to better understand their ecology and to evaluate possible threats at sea. The Atlantic petrel Pterodroma incerta is an Endangered gadfly petrel endemic to the South Atlantic Ocean, with virtually the entire population breeding on Gough Island (Tristan da Cunha archipelago). We describe adult phenology, habitat preferences and at-sea activity patterns for each phenological phase of the annual cycle and refine current knowledge about its distribution, by using light-level geolocators on 13 adults over 1−3 consecutive years. We also ascertained moulting pattern through stable isotope analysis (SIA) of nitrogen and carbon in feathers from 8 carcasses. On average, adults started their post-breeding migration on 25 December, taking 10 d to reach their non-breeding areas on the South American shelf slope. The pre-breeding migration started around 11 April and took 5 d. From phenological data, we found evidence of carry-over effects between successive breeding periods. The year-round distribution generally coincided with the potential distribution obtained from habitat modelling, except during the non-breeding and pre-laying exodus periods, when birds only used the western areas of the South Atlantic. Moulting occurred during the nonbreeding period, when birds spent more time on the water, and results from SIA helped us to distinguish feathers grown around Gough Island from those grown in the non-breeding area. Overall, our results bring important new insights into the spatial ecology of this Endangered seabird, which should help improve conservation strategies in the South Atlantic Ocean.

Temporal and spatial differences in the post-breeding behaviour of a ubiquitous Southern Hemisphere seabird, the common diving petrel

“…These unexpected results indicate that the moult of body feathers was delayed according to the change in breeding phenology. This reinforces the findings showing that the timing of breeding is an important factor in determining the moult schedule of body feathers [ 79 ]. Additionally, a longer post-breeding migration duration lowered the number of isotopic values corresponding to subtropical/neritic waters.…”

Non‐breeding distribution and at‐sea activity patterns of the smallest European seabird, the European Storm Petrel (Hydrobates pelagicus)

“…; Akesson et al 2017, Carneiro et al 2019. A higher variability in the post-nuptial than in the pre-nuptial migration phenology has also been detected in some seabird species (Phillips et al 2006, Ramos et al 2018, Pastor-Prieto et al 2019. Competition for breeding opportunities or access to better nests seem to be the reason given for high synchrony in pre-nuptial migration (Phillips et al 2006), while the main reason pointed out for the greater variability in the timing of post-nuptial migration has been breeding success, as failed breeders usually migrate earlier than successful breeders (Bogdanova et al 2011, Catry et al 2013, Desprez et al 2018, Pastor-Prieto et al 2019.…”

“…2018, Pastor‐Prieto et al . 2019). Competition for breeding opportunities or access to better nests seem to be the reason given for high synchrony in pre‐nuptial migration (Phillips et al .…”

Seabird Migration Strategies: Flight Budgets, Diel Activity Patterns, and Lunar Influence

“…However, the effect is well documented only in the European nightjar Caprimulgus europeaus, in which synchronous movements occurred 11 days after full moonattributed to better foraging conditions during full moon and the time it takes to reach the ideal departure fuel load (Norevik et al, 2019). In seabirds, lunar influences on aerial activity have been mostly demonstrated in relation to foraging (Phalan et al, 2007;Yamamoto et al, 2008;Mackley et al, 2011;Dias et al, 2016;Pastor-Prieto et al, 2019), as moonlight can influence both prey availability (Regular et al, 2011) and prey detectability (Cruz et al, 2013). However, return to the colony of migrant Barau's petrel Pterodroma baraui appeared to be regulated by moonlight (Pinet et al, 2011), and Cory's shearwaters fly more and are more nocturnal on moonlit nights during migration (Dias et al, 2012a).…”