V. Neves

At-sea distribution and trophic ecology of small seabird species (i.e.<100 g) is far less known when compared to their larger relatives. We studied the habitat use (spatial ecology) and isotopic niches (trophic ecology) of the endangered Monteiro's storm-petrel Hydrobates monteiroi during the incubation and chick-rearing periods of 2013. There was a sexual foraging segregation of Monteiro's storm-petrels during the breeding period (tracking data) but also during the non-breeding stage (stable isotope analysis). Females took advantage of their longer wings to forage over the shallower Mid-Atlantic ridge (MAR) north of Azores, under colder and windier regimes when compared to males, who mostly exploited northern deep waters comparatively closer to the breeding colony. Between-sex differences in the spatial distribution were more obvious during the incubation period, with the overlap in their distribution increasing during the chick-rearing phase. There was also an isotopic segregation between sexes both during the previous breeding and the non-breeding stages, with females exhibiting a narrower, lower level isotopic niche when compared to males. Though the distribution patterns reported here should be useful for the at-sea conservation of this endangered species, future research should focus on (1) performing year-round tracking to map the species' distribution during the non-breeding period and (2) gathering multi-year tracking information to understand the effect of inter-annual environmental stochasticity on the foraging choices and trophic habits of the species.

The Roseate Tern, Sterna dougallii, is currently regarded as one of the most endangered seabirds in Europe. The mid-Atlantic Azores islands, Portugal, are an important breeding ground for this species, holding more than 50 per cent of the European population. EU directives are aimed at maintaining and enhancing the current range and breeding numbers of Roseate Tern in the Azores and elsewhere and it is thus a priority species on the Conservation Agenda. However, few studies have examined the Roseate Tern in this geographical area of the Atlantic, and this thesis aims to address this need. The thesis investigates and examines several potential factors affecting breeding numbers of these birds in the archipelago, giving particular attention to predation and potential predators. Data were mainly attained through fieldwork conducted in the period 2002-2004, but investigation of recent historical records of breeding numbers is utilized to assess trends. These historical data were collect...

Predation by the European starling (Sturnus vulgaris) was the main reason for roseate tern (Sterna dougallii) hatching failure on Vila islet, Azores, one of the species’ largest colonies in Europe. Observations showed that single or small groups of starlings were responsible for predation events and that tern nest defence against starlings was generally ineffective. Daily nest survival rate was 94.2% in 2002 and 90.0% in 2003. Nesting success was estimated using a simulation model that allowed for renesting following failure and was 0.42 in 2002 and 0.17 in 2003. These values are considerably lower than the 0.97 nesting success at Rockabill, Ireland, one of the main European colonies, for the period 2000-2003. The sensitivity and importance of the roseate tern population in the Azores are discussed in relation to predation. Management strategies to reduce predation could include non-lethal control of starlings, destruction of starling nests and prevention from nesting in the vicinit...