Status assessment of the Critically Endangered Azores BullfinchPyrrhula murina

Abstract

SummaryThe Azores Bullfinch is endemic to the island of São Miguel (Azores, Portugal). Its status was uplisted to Critically Endangered in 2005 on the basis of an extremely small and declining population that was considered to be restricted to a very small mountain range (43 km 2 ), in a single location, within which the spread of invasive plants constituted a threat to habitat quality. Nevertheless, information was mostly inferred, or the product of, non-systematic studies. In order to carry out a complete assessment of the conservation status we analysed: (i) population trend, calculated from annual monitoring 1991-2008, (ii) population size, and (iii) range size, obtaining estimates in a single morning study in 2008 involving the simultaneous participation of 48 observers. Contrary to previous inferences, the population is no longer decreasing, although quality of laurel forest habitat continues to decline due to the persistent threat of invasive species. Population size (mean 6 SE) was estimated at 1,064 6 304 individuals using distance sampling methods, although the estimate was very sensitive to the survey method used. Range size estimates (extent of occurrence and area of occupancy) were 144 km 2 and 83 km 2 respectively. Given the present information, we propose the downlisting of Azores Bullfinch to Endangered on the IUCN Red List.

The Priolo Atlas: A citizen science-based census initiative for supporting Pyrrhula murina habitat conservation and restoration policies in São Miguel Island (Azores, Portugal)

“…This recent trend and particularly the Atlas of 2008 have been pivotal to support the IUCN decision of downgrading the conservation status of the Azores Bullfinch from critically endangered to endangered (Ceia et al, 2011a). Based on the Atlases results, it has been suggested that the population have slightly expanded (more individuals, higher density and larger distribution area) between 2008 and 2012.…”

“…It became difficult to observe after 1920, and believed to be almost extinct until the 1960s (Bannerman and Bannerman, 1966;Van Vegten, 1968). The historical decline of this endemic species and its present small range (area of occupancy = 83 km 2 ; Ceia et al, 2011a) likely resulted from the widespread clearance of native forest for pastureland and forestry plantations of Cryptomeria japonica, and more recently, the spread of alien invasive plant species (especially Hedychium gardnerianum, Clethra arborea and Pittosporum undulatum; Ramos, 1995Ramos, , 1996aAubrecht, 2000;Ceia et al, 2011a,b;Gil et al, 2011aGil et al, , 2013Gil et al, , 2014 which replace the natural vegetation, suppressing the native biodiversity ) and reducing the regeneration of the natural vegetation (Ceia et al, 2011b;Heleno et al, 2010). The native laurel forest is now restricted to steep slopes, mostly above 400 m of altitude, limiting the Azores Bullfinch distribution which is entirely dependent on native forest for food during most months of the year (Ramos, 1995;Ceia et al, 2011b).…”

“…3), and of the two Priolo Atlases of 2008 and 2012 (Table 1). While such uncertainty on tracking population trends over short term makes it difficult to establish strong causal relationships between ecological management and population dynamics, two general trends can be inferred with confidence from these studies: (1) the population of the Azores Bullfinch has been mostly stable and certainly not declining since 2006; and (2) the population since 2006 is considerably higher than it was in the late 90s, which in turn is considerably higher than it was in the beginning of the last century (Ceia et al, 2011a).…”

“…In this respect we believe that the results of the next years' Atlas will be instrumental, particularly for contrasting the changes on bird density between specific areas subject to habitat management and those that have not been managed. The data collected during the Priolo Atlas has also been used to feed distance sampling approaches (Ceia et al, 2011a) and to develop an innovative stochastic-dynamic modeling approach that allows to predict in silico different conservation scenarios (Bastos et al, 2012).…”

“…This approach might prove extremely useful to detect population trends of rare species which due to the characteristics of their distribution areas cannot be accurately evaluated with classic census techniques. Adapted from Ceia et al (2011a) and Veríssimo (2013). Adapted from Coelho (2014).…”