Abstract
We investigated spatio-temporal distribution patterns of the Critically Endangered Balearic shearwater Puffinus mauretanicus in the northern part of its migratory range, using a combination of effort-corrected land- and boat-based survey data (2007−2010). The species was recorded regularly along the western English Channel (Western Channel) coasts of northwest France and the southwest UK, with peak counts occurring during the summer and autumn months. Foraging aggregations comprising hundreds to thousands of birds (~1 to 20% of the global population) were recorded in the large shallow embayments of northern Brittany in all sur- vey years. Elsewhere, most birds were recorded on passage, with maximum birds-per-hour (BPH) of 169 off northwest France and 36 off the southwest UK. Few birds were recorded offshore, beyond sight of land. A distance-from-shore analysis revealed that the species passed closer to shore than other pelagic seabirds such as sooty shearwater Puffinus griseus. A constant-effort sea- sonal survey from the southwest tip of the UK mainland recorded the species on 93% of survey days, with BPH rates peaking in the morning between 08:00 and 11:00 h. These results have important monitoring and conservation implications for this Critically Endangered species. In par- ticular, the records of large aggregations in spatially restricted areas of the Western Channel dur- ing the inter-breeding period suggests the species could be vulnerable to impacts such as oil spills, or disturbance from offshore construction projects. We also provide evidence that some birds remain in the survey area during the breeding season, suggesting it may be an important site for non-breeding birds.
Highlights
Effective protection of endangered seabirds is facilitated by a comprehensive understanding of the spatio-temporal patterns in their distribution throughout their full range (Phillips et al 2006) and for all age Publisher: Inter-Research · www.int-res.comEndang Species Res 25: 1–18, 2014 and logistical constraints, tracking studies are (1) typically focused on breeding birds, (2) colony specific and (3) only include a small proportion of a species’ population
It is important to recognise the continued value of visual monitoring and the contribution that both opportunistic sighting records and systematic effort-based surveys can make to the understanding of seabird distributions, during the non-breeding season while the birds are at sea
In this study we use effort-corrected sightings data from both opportunistic and dedicated visual monitoring surveys to present an overview of the spatio-temporal distribution and behaviour of the Critically Endangered Balearic shearwater Puffinus mauretanicus within the western English Channel off the southwest UK and northwest France
Summary
Effective protection of endangered seabirds is facilitated by a comprehensive understanding of the spatio-temporal patterns in their distribution throughout their full range (Phillips et al 2006) and for all age Publisher: Inter-Research · www.int-res.comEndang Species Res 25: 1–18, 2014 and logistical constraints, tracking studies are (1) typically focused on breeding birds, (2) colony specific and (3) only include a small proportion of a species’ population. It is important to recognise the continued value of visual monitoring and the contribution that both opportunistic sighting records and systematic effort-based surveys can make to the understanding of seabird distributions, during the non-breeding season while the birds are at sea. Little demographic research has been published since Oro et al (2004); our understanding of the current state of the population is limited and warrants further study Irrespective of these uncertainties, previous research shows an overall decline in the population of the species, evidenced by monitoring at a number of colonies within the species’ limited breeding range on the Spanish Balearic Islands of Mallorca, Menorca, Ibiza and Formentera Irrespective of these uncertainties, previous research shows an overall decline in the population of the species, evidenced by monitoring at a number of colonies within the species’ limited breeding range on the Spanish Balearic Islands of Mallorca, Menorca, Ibiza and Formentera (Fig. S1 in the Supplement at www.int-res. com/articles/suppl/n025p001_supp.pdf) (Oro et al.2004, Ruiz & Marti 2004, Arcos 2011, Arcos et al 2012a)
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