Marques J.T.,University of Lisbon |
Marques J.T.,Institute Desenvolvimento Sustentavel Mamiraua |
Ramos Pereira M.J.,Institute Desenvolvimento Sustentavel Mamiraua |
Ramos Pereira M.J.,University of Aveiro |
And 7 more authors.
Mist netting is a widely used technique to sample bird and bat assemblages. However, captures often decline with time because animals learn and avoid the locations of nets. This avoidance or net shyness can substantially decrease sampling efficiency. We quantified the day-to-day decline in captures of Amazonian birds and bats with mist nets set at the same location for four consecutive days. We also evaluated how net avoidance influences the efficiency of surveys under different logistic scenarios using re-sampling techniques. Net avoidance caused substantial declines in bird and bat captures, although more accentuated in the latter. Most of the decline occurred between the first and second days of netting: 28% in birds and 47% in bats. Captures of commoner species were more affected. The numbers of species detected also declined. Moving nets daily to minimize the avoidance effect increased captures by 30% in birds and 70% in bats. However, moving the location of nets may cause a reduction in netting time and captures. When moving the nets caused the loss of one netting day it was no longer advantageous to move the nets frequently. In bird surveys that could even decrease the number of individuals captured and species detected. Net avoidance can greatly affect sampling efficiency but adjustments in survey design can minimize this. Whenever nets can be moved without losing netting time and the objective is to capture many individuals, they should be moved daily. If the main objective is to survey species present then nets should still be moved for bats, but not for birds. However, if relocating nets causes a significant loss of netting time, moving them to reduce effects of shyness will not improve sampling efficiency in either group. Overall, our findings can improve the design of mist netting sampling strategies in other tropical areas. © 2013 Marques et al. Source
Dias S.,University of Lisbon |
Moreira F.,University of Lisbon |
Beja P.,University of Porto |
Carvalho M.,University of Lisbon |
And 5 more authors.
European Journal of Wildlife Research
The European turtle dove is both a highly valued game species and a species of conservation concern, which is declining due probably to a combination of habitat degradation and unsustainable hunting. Although declines seem to be less severe in the Mediterranean region, it remains uncertain the extent to which ongoing land use changes will negatively affect this species. This study examined this issue, by estimating the effects of landscape composition on the broad scale abundance pattern of breeding turtle doves in continental Portugal. Turtle doves were surveyed in the breeding seasons of 2002 and 2003, from 3160 point counts spaced at about 1-km intervals along 158 transects of about 20 km, evenly covering the country. The frequency of occurrence of turtle doves at each transect was used as a proxy of species abundance, and related using GAM modelling to 21 variables describing land cover and woody linear features (e.g., hedgerows and riparian galleries). Turtle doves were most abundant in north- and central-eastern Portugal, with high abundances also recorded in the regions around Lisbon and along the Guadiana valley. Abundances were positively related to forest cover, particularly by broadleaved forests and by pine stands without woody understory, to cover by permanent crops, and to the density of woody linear habitats. Results suggest that conservation of Mediterranean turtle doves requires policies and management strategies reversing the pervasive trends of forest management neglect and agricultural abandonment, while preserving hedgerows and riparian galleries in more intensive agricultural landscapes. © 2013 Springer-Verlag Berlin Heidelberg. Source