406 research outputs found
Landscape determinants of European roller foraging habitat: implications for the definition of agri-environmental measures for species conservation
Across much of Europe, farmland birds are declining more than those in other habitats. From a conservation perspective, identifying the primary preferred habitats could help improve the foraging conditions of target species and, consequently, enhance their breeding success and survival. Here, we investigated the ranging behaviour and foraging habitat selection of the European roller (Coracias garrulus) during the breeding season in an agricultural landscape of South Iberia. The occurrence of foraging rollers was predicted to gradually increase with decreasing distance from the nest and increasing availability of perches, such as fences and electric wires. Traditional olive groves and stubble fields were positively and negatively associated with the occurrence of rollers, respectively. Additionally, analysis of hunting strikes showed that rollers highly prefer foraging in fallows rather than cereal or stubble fields. Prey surveys revealed that fallows had the highest abundance of grasshoppers, rollers’ preferred prey during chick-rearing. Pair home-ranges, obtained from 95% fixed Kernel estimators averaged 70.9 ha (range = 34–118 ha) and most foraging trips (80%) occurred in the close vicinity of the nest (<500 m). Number of chicks fledged was not affected by mean foraging distances travelled during the chick-rearing period. Overall, our results suggest that traditional extensive practices of cereal cultivation, with large areas of low-intensity grazed fallows, represent a high-quality foraging habitat for rollers and should be promoted through agri-environmental schemes within at least 1-km radius from the nest. These recommendations are targeted at the roller, but have been shown to apply broadly to several other steppe-bird species
Green turtles highlight connectivity across a regional marine protected area network in west Africa
Networks of marine protected areas (MPAs) are invaluable for the protection of species
with high dispersal capacity, yet connectivity within networks is poorly understood. We
demonstrate the connectivity within the regional MPA network in West Africa (RAMPAO),
mediated by the largest green turtle population in the eastern Atlantic Ocean. We
equipped with satellite tags 45 female green turtles nesting in the Bijagó
s Archipelago,
Guinea-Bissau, and tracked them during internesting, migration, and foraging to quantify
the degree of coverage the RAMPAO network provides during each of these critical
periods. During the internesting period, turtles were largely concentrated around the
nesting islands, with a mean of 94.8% (SD 0.1%, range: 46% - 100%, n = 40 turtles) of
tracking positions falling within MPA limits. Among the 35 turtles successfully tracked into
the foraging period, we identified variable migratory strategies, with 12 turtles remaining
near-resident at distances of 40-90 km from breeding sites, 10 turtles migrating 300-400
km to The Gambia and Senegal, and 13 turtles traveling >1000 km to northern Mauritania.
Of the 35 foraging turtles, 26 used MPAs, with a mean of 78.0% (SD 34.8%, range: 3.7% -
100%) of their tracking positions falling within the limits of RAMPAO MPAs, across
Guinea-Bissau, Senegal and Mauritania. Migration corridors with high concentrations of
passing turtles were mostly located nearshore, and 21% of these high passage areas fell
within the MPA network. Overall, we found that this population connects five RAMPAO
MPAs, yet some foraging sites (e.g., in the Bijagó
s) and important migration areas (e.g.,
Cap-Vert peninsula) described here are currently unprotected. These results are relevant
to any considerations of MPA extension or establishment within the regional network,
which would contribute towards meeting the Convention on Biological Diversity targets for
national marine protected area estate coverage. By documenting biological connectivity
across RAMPAO, this study represents an important example of the relevance of
international protected area networks for green turtle conservation and for wider
conservation action at a regional scale.Fundação para a Ciência e Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio
Are blackcaps sylvia atricapilla differential distance migrants by sex?
Aims: To investigate if male and female blackcaps show differences in the amplitude of migratory
movements.
Methods: The extent of movements of male and female British blackcaps were analysed using ringing recovery
records. Furthermore, through a literature review and the collection of original field data, the
sex-ratios of blackcap samples taken at several latitudes in Europe and Africa were compared.
Results: There were no differences between British male and female blackcaps in relation to wintering
latitude or distance moved during migration. Sex-ratios of blackcap samples were quite even across a wide
range of latitudes. However, there was a significantly larger proportion of females in samples of birds that
wintered in Africa.
Conclusions: Laboratory data and morphological studies have yielded inconclusive results in relation to
the question of whether or not European blackcaps are differential distance migrants. The results from the
present study suggest that British blackcaps are not differential distance migrants. Furthermore, there is,
at best, only a weak latitudinal segregation of the sexes of blackcaps wintering in Europe and Africa. The
slightly higher proportion of males in European samples, when compared to Africa, could result from a
differential behaviour of males and females in some blackcap populations, or simply result from differences
in the sex-ratios of blackcap populations breeding and wintering in different areas. An absence of
a pronounced latitudinal segregation in the size-monomorphic blackcap is interesting, and contrasts
with the pattern found in more sexually dimorphic species, such as the chiffchaff Phylloscopus collybita
or the robin Erithacus rubecula
Albatrosses Following Fishing Vessels: How Badly Hooked Are They on an Easy Meal?
Fisheries have major impacts on seabirds, both by changing food availability and by causing direct mortality of birds during trawling and longline setting. However, little is known about the nature and the spatial-temporal extent of the interactions between individual birds and vessels. By studying a system in which we had fine-scale data on bird movements and activity, and near real-time information on vessel distribution, we provide new insights on the association of a threatened albatross with fisheries. During early chick-rearing, black-browed albatrosses Thalassarche melanophris from two different colonies (separated by only 75 km) showed significant differences in the degree of association with fisheries, despite being nearly equidistant to the Falklands fishing fleet. Most foraging trips from either colony did not bring tracked individuals close to vessels, and proportionally little time and foraging effort was spent near ships. Nevertheless, a few individuals repeatedly visited fishing vessels, which may indicate they specialise on fisheries-linked food sources and so are potentially more vulnerable to bycatch. The evidence suggests that this population has little reliance on fisheries discards at a critical stage of its nesting cycle, and hence measures to limit fisheries waste on the Patagonian shelf that also reduce vessel attractiveness and the risk of incidental mortality, would be of high overall conservation benefit
Differential migration of chiffchaffs Phylloscopus collybita and P. ibericus in Europe and Africa
Differential migration is a widespread, but poorly understood, phenomenon in birds. In
this paper, we present the first detailed field study of differential migration in the Old
World warbler (Sylviidae) family. We studied two chiffchaff Phylloscopus [collybita ]
semispecies: the common chiffchaff P. [c. ] collybita and the Iberian chiffchaff P. [c. ]
ibericus. Using data collected at several latitudes in Europe and Africa, we present
convincing evidence for differential distance migration of sexes in chiffchaffs, with
females moving further than males. Interestingly, while there was a pronounced
gradient in the sex-ratios in Europe and North Africa (with an increasing proportion of
females with declining latitude), no clear pattern was found south of the Sahara, where
sex-ratios were more male-biased than predicted by a simple latitude model. This
suggests that, amongst the chiffchaffs wintering in West Africa, a large proportion is
composed by Iberian birds, and provides support to previous suggestions that Iberian
chiffchaffs are long distance migrants. Results from detailed studies in Senegal also
show that chiffchaffs display differential timing of spring migration, with males leaving
the winter quarters considerably earlier than females. The results are discussed in the
framework of the three main (non-mutually exclusive) hypotheses attempting to explain
the latitudinal segregation of the sexes. Given the relative failure of standard
comparative studies to discriminate between competing single-factor hypotheses to
explain differential migration, it is argued that the chiffchaff species complex might be
particularly suited to study this issue using a new approach suggested by Cristol et al.
(1999): detailed (further) comparisons between closely related species (such as the
common and the Iberian chiffchaffs) could help identifying the key factors to be
incorporated into optimality models that can predict relative distance of migration of
different sex or age classes
Factors affecting post-fire crown regeneration in cork oak (Quercus suber L.) trees
Cork oak (Quercus suber) forests are acknowledged
for their biodiversity and economic (mainly cork
production) values. WildWres are one of the main threats
contributing to cork oak decline in the Mediterranean
Basin, and one major question that managers face after Wre
in cork oak stands is whether the burned trees should be
coppiced or not. This decision can be based on the degree
of expected crown regeneration assessed immediately after
Wre. In this study we carried out a post-Wre assessment of
the degree of crown recovery in 858 trees being exploited
for cork production in southern Portugal, 1.5 years after a
wildWre. Using logistic regression, we modelled good or
poor crown recovery probability as a function of tree and
stand variables. The main variables inXuencing the likelihood
of good or poor crown regeneration were bark thickness,
charring height, aspect and tree diameter. We also
developed management models, including simpler but easier
to measure variables, which had a lower predictive
power but can be used to help managers to identify, immediately
after Wre, trees that will likely show good crown
regeneration, and trees that will likely die or show poor
regeneration (and thus, potential candidates for trunk
coppicin
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