José Luis Tellería

HISTORICAL DIVERSIFICATION OF MIGRATION PATTERNS IN A PASSERINE BIRD

Abstract Migratory strategies of birds require complex orientation mechanisms, morphological adaptations, and life‐history adjustments. From an evolutionary perspective, it is important to know how fast this complex combination of traits can evolve. We analyzed mitochondrial control‐region DNA sequences in 241 blackcaps (Sylvia atricapilla) from 12 populations with different migratory behaviors. The sample included sedentary populations in Europe and Atlantic archipelagos and migratory populations with different distances of migration, from regional to intercontinental migrations, and different heading directions (due to a migratory divide in central Europe). There was no genetic structure between migratory and sedentary populations, or among populations from different biogeographic areas (Atlantic islands, the Iberian Peninsula, or the continent), however we found evidence of a genetic structure when comparing populations located on either side of the migratory divide. These findings support an independent evolution of highly divergent migratory strategies in blackcaps, occurring after a postglacial colonization of the continent along western and eastern routes. Accordingly, mismatch‐distribution analyses suggested an expansion of blackcaps from a very small population size, and time estimates dated such an expansion during the last postglacial period. However, the populations in Gibraltar, located in a putative Mediterranean refuge, appeared to be independent of these processes, showing evidence of restricted gene flow with other populations and demonstrating insignificant historical changes in effective population size. Our results show that the interruption of gene flow between migratory and sedentary populations is not necessary for the maintenance of such a polymorphism, and that even the most divergent migratory strategies of a bird species are susceptible to evolution in response to historical environmental changes.

Effects of human disturbance on spatial and temporal feeding patterns of Blackbird Turdus merula in urban parks in Madrid, Spain

We studied how human presence in three urban parks in Madrid (Spain) might affect Blackbird densities by changing feeding behaviour patterns. Our specific purposes were: (a) to ascertain the effect of park visitors on Blackbird feeding behaviour; (b) to analyse the influence of human disturbance on foraging success; and (c) to determine how humans affect Blackbird spatial and temporal patterns of habitat use. Pedestrians were the main source of flushing responses in all sampled parks, followed by Magpies Pica pica and dogs accompanying visitors. Blackbird responses to visitors entailed more time being vigilant and moving away from people and less time searching for food (decreasing food intake), a response that remained constant in the three parks. The number of pedestrians was positively correlated with Blackbird distance to pathways and negatively correlated with distance to protective cover. The number of active birds decreased with increase in the number of pedestrians during the day. Blackbird density was negatively related to the number of visitors per park. Our results confirmed that human disturbance negatively affects Blackbird feeding strategies in urban parks, ultimately modifying spatial and temporal patterns of habitat selection and abundance. Since such responses could also affect densities of other urban species by the same process, we propose some management measures to decrease the levels of disturbance as well as to enhance the recreational use of urban parks.

Factors Affecting the Distribution of a Waterbird Community: The Role of Habitat Configuration and Bird Abundance

Abstract The effects of the environmental and species’ characteristics were analyzed for the richness and distribution of the dabbling and diving waterbirds in a wetland complex with 26 ponds (0.1-88.6 ha) in southeast Spain. These environments are being lost on a global scale through human activity. Morphological, geographical, hydrochemical, vegetative and temporal parameters of the ponds (11 in total), as well as characteristics of the species, were sampled to identify those variables with the capacity to predict the effects provoked by the habitat configuration. The function of the size and the isolation, as variables related to the habitat patchiness, as well as the development of the emergent vegetation of the wetlands were discriminated as forecasters of number of species. The avian abundance had an important role in the capacity of the birds to occupy ponds (sampling hypothesis). The differences in the abundance of species probably favored their orderly loss from the wetland complex at the same rate as the ponds diminished in size (“nested” pattern). The results obtained imply the need for the conservation or restoration of numbers of wetlands, paying special attention to the largest, with peripheral vegetation cover around large, open water bodies in complexes with more than one pond, to preserve the greatest number of species against the loss of wetlands which is occurring worldwide and is a cause of biodiversity decline.

Bird conservation in fragmented Mediterranean forests of Spain: effects of geographical location, habitat and landscape degradation

Abstract The effects of habitat fragmentation on forest bird assemblages were analysed in 214 holm oak ( Quercus ilex ) remnants spread across the northern and southern plateaux of central Spain. Bird richness was highly dependent on fragment area for all species regardless of isolation, and barely affected by habitat traits. Geographical location was associated with high differences in richness of bird assemblages, which included 17 species exclusive to northern remnants and one exclusive to southern remnants. This supports the hypothesis that habitat suitability deteriorates sharply from north to south for forest birds in Spain. The species-area relationships of bird assemblages sampled in fragmented forests along a broad continental gradient (from Norway to southern Spain) showed that true forest birds only nest in woodlands >100 ha in southern Spain, whereas the full complement of forest species occurs in much smaller fragments in central-western Europe. Loss of species that are particularly sensitive to habitat fragmentation accounts for these differences between dry Spanish and mesic European woodlands. These results are explained by the low habitat suitability of Spanish woodlands, associated with the restrictive conditions for plant regeneration in the Mediterranean climate and long-standing human usage. There is, therefore, a particular need to develop management strategies that conserve birds, and probably other forest organisms, in Mediterranean regions by preventing habitat deterioration and decreases in fragment size, and by conserving all woods >100 ha.

Effects of forest fragmentation on a guild of wintering passerines: the role of habitat selection

Abstract This study analyses the winter colonization of an archipelago of 31 forests (0·1–350 ha) in central Spain by the guild of pariforms ( Parus, Aegithalos, Regulus, Sitta and Certhia ). Two hypotheses are considered: (a) that birds with similar habitat preferences tend to disappear simultaneously with the reduction in forest size, leading to a ‘nested’ pattern of species distribution; or (b) that the species in the smallest forests are a random sample of those found in the larger ones. The results support hypothesis (a). The species that depend on relatively scarce resources, such as tree trunks and junipers Juniperus thurifera ( Sitta europaea, Certhia brachydactyla, Parus cristatus and P.ater ) only occupied the largest forests. On the other hand, species that exploit abundant, ubiquitous resources, such as holm oak Quercus ilex foliage ( Regulus ignicapillus and Parus caeruleus ), were distributed uniformly throughout all the fragments. These results emphasize the need for a better understanding of habitat selection by species when designing conservation strategies for fragmented populations.

A comparison on the response to forest fragmentation by medium-sized Iberian carnivores in central Spain

We studied the use of forest fragments by five medium-sized carnivorespecies in 280 forest fragments on the two Iberian plateaus. We looked forindirect evidence (faeces, tracks, dens) of fragment use (occurrence) by thespecies and analysed whether occurrence could be related to four groups ofvariables: local (vegetation structure and patch size), landscape (distance topossible colonisation sources), regional (fragment location on the northern orsouthern plateau) and the vegetation type of the fragments. We analysed thedifferential response of species according to their life-history and behaviouraltraits. The relationship between use by each species and the factors studied wasanalysed using stepwise logistic regressions. Results indicate that threefactors are crucial to explain fragment use: fragment size, geographic locationand vegetation type. Large fragments are used more than smaller ones, thenorthern plateau is more suitable than the southern plateau, and holm oak andbroad-leaved oak forests are more used than pine woods. The effects andmagnitude varied slightly among species, depending on habitat requirements orlife-history traits. Data indicate that conservation strategies in fragmentedenvironments must take into account elements functioning at different spatialscales, and that it is essential to consider each case within a characteristicregional context.

Abundance and Food-Searching Intensity of Wood Mice (Apodemus sylvaticus) in Fragmented Forests

Abundance, food-searching intensity, physiological status, and population attributes of wood mice ( Apodemus sylvaticus ) were studied in forest islands of central Spain. Seventeen isolated woodlots ( Quercus rotundifolia ) ranging from 0.1 to 280 ha were studied. The results show high densities of mice and high rates of predation on acorns in the smaller forests.

Stopover site fidelity of four migrant warblers in the Iberian Peninsula

This paper analyses by means of ringing data the stopover site fidelity of four warbler species (Sylvia atricapilla, Sylvia borin, Phylloscopus collybita and Acrocephalus scirpaceus) during their migrations across the Iberian Peninsula. The mean recovery rates observed during migration periods (mean 0.28, range 0-0.54) were around 50% of the ones observed during the breeding and wintering seasons (mean 0.51, range 0.41-0.58). These differences in recovery rate were statistically significant in all species but Acrocephalus scirpaceus. This warbler, with its more restricted habitat requirements, showed higher recovery rates during the spring and autumn migration periods confirming the hypothesis that species depending on scarce, patchily distributed stopover habitats during their migrations show stronger stopover site fidelity during their journeys. Our results support the view that some migrant species actively select stopover sites during their migrations.

Morphometric variation of five Iberian Blackcap Sylvia atricapilla populations

This paper analyses the variation of several morphological traits in five populations of Blackcaps Sylvia atricapilla distributed along a latitudinal gradient in the Iberian peninsula. The northern and central populations differ from the southern ones in their longer and more pointed wings, narrower bills, shorter tarsi and smaller body size. These features define two morphological groups and correlate with differences in their migration and feeding habits. Birds from northern and central Iberia breed in habitats with harsh winter conditions, which they abandon in autumn when they migrate to their wintering grounds. Birds from the mild, southern sectors remain there throughout the winter. Their migratory behaviour, and a stronger specialisation for feeding on foliage invertebrates, could explain the morphological differentiation of northern Blackcaps relative to southern ones. Our results suggest that the Iberian migratory populations might have descended from ancestral, southern-like ones, that have become adapted to exploit their seasonal breeding grounds.

Distributional patterns of insectivorous passerines in the Iberian Forests: does abundance decrease near the border?

In this paper we analyse whether the abundance of breeding insectivorous birds decreases towards the South along the Iberian forests (as predicted by the model of Brown (1984)), and try also to relate these changes of abundance to several environmental features. Abundances of six foliage insectivorous passerines that are not tree-hole nesters, Troglodytes troglodytes (L., 1758), Erithacus rubecula (L., 1758), Sylvia atricapilla (L., 1758), Phylloscopus collybita (Vieillot, 1817), Regulus ignicapillus (Temminck, 1820), and Aegithalos caudatus (L., 1758) were recorded in fifty-eight large woodlands along a 850 km belt crossing the Iberian Peninsula. By means of simple, partial and stepwise multiple regression analyses bird abundances were related with distances to the north of each woodland and with the mean scores of climatic (mean temperature and precipitation), physiognomic (tree trunk densities under 20 cm diameter and over 30 cm) and floristic (conifer v. broadleaved tree species) variables. Five of the six species showed significant, negative correlations between their abundances and the distances of forests to the north, thus corroborating Browns model. A. caudatus did not show, however, any clear pattern of abundance distribution. Simple correlation analyses showed also the importance of climatic and physiognomic variables in predicting bird abundance. When the problem of interaction between variables was solved, all the five species showed significant positive partial correlation with precipitation, although distance continued to be important for three species (T. troglodytes, R. ignicapillus and P. collybita), suggesting some additional role of this variable in the processes involved in the observed distribution. The importance of precipitation and distance to the north as predictors of abundance was also showed by the stepwise regression analysis. The mean variance explained by these models was around 30%, higher than or similar to that obtained in other studies performed at the local or intrahabitat level. This suggests the potential usefulness of multivariate approaches in studies of bird distribution undertaken on large scales.