Several attempts have been performed to study this complicated issue, for example Wade & Hickey (2008) used a combination of satellite imagery processing that were statistically compared with data collected in the field, mapped according to locations of birds’ preferred food in an aquatic environment, with the aim to prioritize research and conservation efforts in these areas. Oguchi, Smith & Owen (2017) affirm that migrating birds can improve their immune and antioxidant status during stopover, implying that variation in stopover habitat can affect migrants’ health and underlining the importance of stopover site ecological conservation. Therefore, seasonally abundant fruits can be a significant food resource for migrating songbirds in temperate regions ( Parrish, 1997 White, 1989 Smith et al., 2007). Experimental removal of available fruits decreased local abundance of autumn migrants ( Parrish, 2000) and birds overwintering ( Borgmann et al., 2004). Migrant species captured in autumn had significantly greater body masses and greater daily rates of body mass gain at sites where fruits were available compared to those of birds taken at sites without fruits ( Ferns, 1975 Thomas, 1979 Bairlein, 2002). (2004), underlining the role of stopover sites for the diet of migratory birds, stressed that the quality of the food available at stopover sites can be dramatically important. Finding food during the migration route is extremely important for many migratory species and can affect their migration success, pattern and timing ( Drent, Fox & Stahl, 2006 Newton, 2006 Vilkov, 2013 Wolfe, Johnson & Ralph, 2014).Īlthough many associate migration with migratory flight, according to Hedenström & Alerstam (1988), most of the migration period is spent stationary at successive stopover sites where birds spend their time resting and foraging as they rebuild protein and energy stores in preparation for their next migratory flight. They can be well delimited spots like a lake or a marsh for water birds ( Downs & Horner, 2008) or can be more widely distributed along a gradient of environments like a combination of different forest vegetation types located following the orientation of an alpine valley. The habitats or natural communities that provide migrants with the opportunity to refuel and rest during their journey are commonly known as stopover sites. This is due both to scarce vegetation data availability and to an imprecise knowledge of bird migration paths.
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The relation between migration paths and trophic availability en route is particularly difficult to study, since it is difficult to model food availability on the terrain ( Drent, Fox & Stahl, 2006 Ma, Li & Chen, 2005 Moore & Woodrey, 1999 Gyimóthy et al., 2011). Different works studied migration paths and birds features taking into account various parameters ( Chevallier et al., 2010 Vilkov, 2013 Bauer, Ens & Klaassen, 2010). Although migration is increasingly studied, many factors that influence migratory flows and routes still remain unknown or poorly understood ( Bairlein, 2003 Bairlein, 2008). The maps created and distributed along this work can be useful to address more detailed studies about stopover sites as well as the spatial ecology of other fruit eating animals.īird migration is one of the most extraordinary natural phenomena that has always fascinated humans and stimulated researchers curiosity. The highest fruit availability in the study area during September and October co-occurs with the peak of captures of berry eating birds. The presence and coverage of the plant species was modelled with the geo-statistical method of the Gaussian Kernel, which was validated against the ground truth of field sampling data with a correct classification power above 80% in most cases.
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Cornus mas new haven ct series#
We created a unique database that contains information on the presence and periods of fructification of 52 wild plants carrying berries and a series of original cartographic themes. This work presents a GIS-database approach that combines spatial and non-spatial ecological information in order to map fruit availability from vegetation over time in the SE Alps, an important node of European migratory routes. Food availability en route is particularly important for many species and can affect their migration success, pattern and timing but this relationship has not been addressed at a wide scale due to the lack of spatial models of food availability on the terrain. Bird migration is a widely studied phenomenon, however many factors that influence migratory flows remain unknown or poorly understood.