Navedo J.G.,University of Extremadura |
Arranz D.,Aves Cantabricas SL. |
Herrera A.G.,Aves Cantabricas SL. |
Salmon P.,Aves Cantabricas SL. |
And 2 more authors.
Biodiversity and Conservation | Year: 2013
Coastal pastures are common agroecosystems adjacent to estuarine areas that can provide valuable habitat for wildlife, particularly for migratory shorebirds. Disentangling the factors that influence coastal pasture use by wintering shorebirds will provide new insights into its role for buffering human disturbances and habitat loss in intertidal areas. We examined whether numbers of two shorebirds (Eurasian curlew and Black-tailed godwit) foraging actively on coastal pastures was affected by weather conditions, tidal stage (low/high tide) and number of harvesters at intertidal areas throughout winter. Both species frequently used coastal pastures and most individuals foraged actively there. The average percentage of the total wintering population of curlews and godwits foraging on coastal pastures was 27.4 and 7.8 %, respectively, and was significantly higher during high tide compared to low tide. The number of harvesters on mudflats also had a positive significant effect in explaining the presence of curlews, and to a lesser extent for godwits, on coastal pastures, and accumulated rainfall had a positive effect for both species too. These supratidal areas were consistently used as alternative foraging grounds during low tide by curlews, as well as supplementary foraging areas during high tide by wintering populations of both large shorebirds. By supplementary foraging, wintering curlews, and probably godwits, seemed to compensate for a negative effect of the presence of harvesters on their foraging activity. We recommend managing of those coastal agricultural fields adjacent to intertidal foraging grounds in order to increase the availability of supratidal foraging habitats for declining shorebird populations. These habitats may thus have a beneficial role in sustaining populations of wintering shorebirds, but further studies are needed to estimate if birds can compensate for any shortfall in daily energy budget by supplementary foraging on coastal pastures, thus providing insights into whether they are involved in large-scale population regulation of migratory birds. © 2013 Springer Science+Business Media Dordrecht.
Navedo J.G.,University of Extremadura |
Navedo J.G.,National Autonomous University of Mexico |
Herrera A.G.,Aves Cantabricas SL.
Journal of Coastal Conservation | Year: 2012
In coastal wetlands, the increasing level of disturbance from recreational activities could threaten waterbird populations, which overall are showing decreasing trends. Despite the crucial contribution of waterbirds to biodiversity, empirical studies measuring the effects of disturbance on them remain scarce, especially in terms of the impact upon their roosting sites. We developed an experimental treatment to measure the effects of a pedestrian walking on a site used by overwintering waterbirds in a wetland of international importance. We registered 156 events (88 at high tide) of flushing birds, totaling 4,018 individuals. Each treatment drove the flushing of 1-5 % of the wintering populations of nearly all species present during high tide. In addition, 1. 5 % of the Eurasian curlew wintering population was driven to change site. All the effects were found to be reduced during other tidal periods. Therefore, allowing recreational use in a previously undisturbed area can systematically increase daily energy expenditure of significant percentages of different waterbird populations during high tide, and even cause birds to avoid a site completely. These effects will probably be even worse given that our results were derived only from a disturbance source of low magnitude and frequency. We recommend that, prior to developing recreational areas close to the shoreline, coastal wetland managers should study the habitat use of waterbirds during high tide in relation to total waterbird populations using the wetland. © 2012 Springer Science+Business Media B.V.