Integrating individual habitat choices and regional distribution of a biodiversity indicator and top predator

Abstract

Aim Habitat selection studies have mainly focused on behavioural choices of individuals or on the habitat‐related regional distribution of a population, with little integration of the two approaches. This is despite the fact that traditional biogeography theory sees the geographical distribution of a species as the collective outcome of the adaptive habitat choices of individuals. Here, we integrate individual habitat choices with regional distribution through a bottom‐up Geographical Information System (GIS)‐based approach, by using a 9‐year data set on a large avian predator, the eagle owl (Bubo bubo L.). We further examine the potential population level and biodiversity consequences of this approach. Location The study was conducted in the Trento Region (central‐eastern Italian Alps) and in six other areas of the nearby Lombardia Region in the central Alps. Methods We used stepwise logistic regression to build a habitat suitability model discriminating between eagle owl territories and an equal number of random locations. The model was applied to the whole Trento region by means of a GIS so as to predict suitable habitat patches. The predicted regional distribution (presence–absence in 10‐km grid quadrats) was then compared with the observed one. Furthermore, we compared estimates of biodiversity in quadrats with and without eagle owls, so as to test whether the presence of this top predator may signal macro‐areas of high biodiversity. Results The logistic habitat suitability model showed that, compared with a random distribution, eagle owls selected low‐elevation breeding sites with high availability of prey‐rich habitats in their surroundings. Breeding performance increased with the availability of prey‐rich habitats, confirming the adaptiveness of the detected habitat choices. We applied the habitat suitability model to the 6200 km2 study region by means of a GIS and found a close fit between the observed and predicted regional distribution. Furthermore, population abundance was positively related to the availability of habitat defined as suitable by the above analyses. Finally, high biodiversity levels were associated with owl presence and with the amount of suitable owl habitat, demonstrating that modelling habitat suitability of a properly chosen indicator species may provide key conservation information at the wider ecosystem level. Main conclusions Our bottom‐up modelling approach may increase the conservation‐value of habitat selection models, by (1) predicting local and regional distribution, (2) estimating regional population size, (3) stimulating further hypothesis testing, (4) forecasting the population effects of future habitat loss and degradation and (5) aiding in the identification and prioritization of high‐biodiversity areas.

Adaptive range selection by golden eagles in a changing landscape: A multiple modelling approach

“…Compared to randomly located ranges, eagles selected ranges well-spaced out, characterised by a rugged topography and rich in main prey species and in open habitats favoured by their main prey species, such as grassland, shrubs, xerophytic vegetation and rocky outcrops. The selection for Table 5 -Multiple regression models (GLM with normal errors and an identity link function) testing the effect of environmental variables on prey availability, nest spacing and productivity of a golden eagle population (n = 43 territories) in the Trento region of the central-eastern Italian Alps overdispersion is a common feature of solitary, territorial raptors with a regular dispersion of nest-sites (e.g., Sergio et al, 2004aSergio et al, ,b, 2005b. Such spacing behaviour may allow population density to be fine-tuned to resource availability, while simultaneously minimizing intraspecific competition (e.g., Newton, 1979;Village, 1983).…”

Diversity and Nest Characteristics of Owl Species Inhabiting Margalla Hills National Park Islamabad, Pakistan

“…They are wide spread geographically; however, only a few areas are inherently species-rich. Owl biodiversity serves as a good bio-indicator for ecosystem health and conservation efforts that target owl species inherently protect many other species, habitat, and ecological functions (Caro and O' Doherty, 1999;Sergio et al, 2004;Movalli et al, 2008). They are found in forests which are not intruded by human beings, abandoned old buildings and barns.…”

“…The list of owl species has grown from 144 species (Peters, 1940) to 211 species in 2012 (Gill and Donsker, 2012). The International Union for the Conservation of Nature (IUCN) has listed the status of 32 owl species as "Vulnerable" to "Critically Endangered", 22 species as "Near Threatened" and other 27 have either not been evaluated or do not have sufficient data to assign a status (Sergio et al 2004;Movalli et al 2008). Out of 20 owl species occurring in Pakistan, four species were already known from Margalla Hills National Park (MHNP), viz., Himalayan Barred owlet (Glaucidium cuculoides), Oriental Scops owl (Otus sunia), Pallid Scops owl (Otus brucei) and Tawny owl (Strix aluco) (Robrets, 1991).…”

“…The greatest threat to owls is the loss of habitat, though they are also negatively impacted by pesticide use, vehicle collisions and illegal trade (Konig et al, 1999;Sergio et al, 2004;Ahmed, 2010). Although studies related to ecology of many other bird species have been conducted in Pakistan such as by Abdullah et al (2017), however, different owl species, mainly have stayed neglected for their ecological investigations.…”

Breeding season habitat selection by Ferruginous Pygmy OwlsGlaucidium brasilianumin central Argentina

“…We believe that the relatively high abundance of owls in the xerophytic ecosystem (67% of our sampled locations) should be further investigated owing to the potential role of top predators as reliable indicators of biodiversity values. In fact, solid evidence exists of the association between apex predators that belong to higher trophic levels and habitat complexity, community richness and biodiversity levels (Sergio et al 2004;Sergio et al 2005, Sergio et al 2006. Specifically, this latter relationship has been successfully tested for Glaucidium passerinum, the European counterpart of the Ferruginous Pygmy Owl, providing clear evidence of general patterns of association between charismatic top predators and biodiversity (Sergio et al 2006).…”