Francisco Campos

River channelization effects on fish population structure in the Larraun river (Northern Spain)

As a consequence of the construction of the A-15 highway between 1991 and 1995, some modifications affecting the Larraun River (Navarra, North of Spain) were made. One of the most important effects was the channelization of a section of the river in the middle zone. Fish were caught by electrofishing in August of 1996 in the channelized reach, as well as in non-modified stretches upstream and downstream. Physical and chemical variables and shelter availability were also analyzed. The captured fish were measured (total length) and released into the river. We calculated the density, biomass, length distribution and diversity, comparing the obtained results from the different stretches. The number of species was higher in the lower zones of the river and diversity increased progressively downstream. The fish density in the channelized section was slightly lower than in the other two points. Also biomass in the channelized section was about a factor of 10 smaller than the calculated biomass in unaltered points. Moreover, in comparison with the unaltered sections of the river, in the channelized area a major decrease in the presence of fish larger than 150u2009mm was detected. The low shelter availability in the channelized section, lack of bank vegetation and alterations in the substratum could explain the observed variations in the length distribution, biomass and the lower value of the density of European minnow, Phoxinus phoxinus (Linnaeus, 1758).

Breeding Success of Southern Grey Shrikes Lanius meridionalis in Agricultural Areas: The Influence of Nest Site Characteristics

Abstract. n Three hundred and thirty nests of Southern Grey Shrike Lanius meridionalis were located during 1998–2010 in two highly fragmented Mediterranean agricultural areas of Spain (Olite in Northern and Toro in Western part of the country). Most nests (ca. 85%) were built in thorny shrubs (mainly Dog Rose Rosa sp. and Blackberry Rubus ulmifolius) and thornless shrubs (mainly Holm Oak Quercus rotundifolia and Kermes Oak Quercus coccifera). Based on a logistic regression, three factors had an influence on breeding success: study area, breeding phenology, and plant cover type. Location of the nest inside the shrub, as well as luminosity inside a shrub varied between studied shrub species, but did not significantly affect breeding success. The percentage of successful nests was significantly higher in Olite than in Toro (64.5% and 37.9% respectively). In Olite, but not in Toro, clutches laid early (first egg laid prior to 1st May) were more successful than clutches laid late. The highest breeding success was recorded in nests located in thorny shrubs and, especially, in those found in Blackberry bushes. Conservation of Blackberry shrubs appears to be an appropriate measure to increase breeding success of the Southern Grey Shrike.

Usefulness of Biometrics to Analyse Some Ecological Features of Birds

Morphometric measurements of birds are the first data to be really considered as biometric in this discipline. Baldwin et al. (1931) depicted and explained in detail the external measurements used in ornithology. Currently, many of these measurements have been forgotten or are rarely used both in books dedicated to bird taxonomy (Cramp & Simmons, 1977) and in field guides on different geographical areas or on large bird groups such as shorebirds, raptors, passerines, etc. (Svensson, 1992; Baker, 1993). Old biometric analyses used measurements performed on birds preserved in natural history museums. An appropriate representation of specimens is generally found in these museums, both in numbers (which allows for a large sample size) and in geographic origin (which enables the establishment of comparisons between birds of different areas) (Jenni & Winkler, 1989; Winker, 1993, 1996). Body mass was another one of the data used in the initial biometric analyses. Its objective was to determine the presence of daily or seasonal variations, or variations linked to other specific periods: breeding, rearing and migration. The next step was the establishment of a link between metric differences and the sex of birds. In some species, these differences were very visible and therefore statistical analyses were not required to support the distinction between males and females as in some raptors such as the Merlin Falco columbarius (Newton, 1979; Wiklund, 1990), owls and skuas (Andersson & Norberg, 1981). Similarly, marked biometric differences between bird populations of the same species found in different geographical areas were recorded (Svensson, 1992). This resulted in the identification of subspecies when these populations were geographically isolated, not sharing potential hybridization areas. Thus, for example, 10 subspecies of the Bluethroat Luscinia svecica have been identified throughout Europe, Asia and Alaska (Collar, 2005), a further 10 subspecies of Southern grey shrike Lanius meridionalis have been identified (Lefranc & Worfolk, 1997; Klassert et al., 2007), etc. Substantial databases were created as a result of the routine collection of a minimum number of measurements when a bird was captured, this information being used for specific purposes. Possibly, the existence of these data and the ability of observation lead researchers

Morphological and Biometric Features of Male Bluethroats Luscinia svecica in Central Iberia

Summary. n In order to test biometrics and plumage variability in bluethroats Luscinia svecica in central Iberia, 185 birds were captured in four areas (Sierra-Béjar, Sierra-Piedrahita, Sierra-Gredos and Sierra-Paramera). Older bluethroats were significantly larger than second calendar year birds in wing, tail, and total body lengths, but not in tarsus and bill lengths. A multivariate analysis of variance (MANOVA) and a principal component analysis (PCA) were used. Total body length only varied significantly between sampling areas: the birds from Sierra-Béjar were larger than those from Sierra-Gredos and Sierra-Paramera, but were similar to those of Sierra-Piedrahita. Birds with a white spot, a chestnut spot or no spot were found. Therefore, the question arises whether there are three subspecies (L. s. cyanecula, L. s. svecica and L. s. azuricollis), or three forms of a single subspecies (L. s. azuricollis). The percentage of birds with and without a throat spot was similar in the four sampled areas, and the percentage of birds with a spot significantly increased with age. These observations suggest that some plumage characters, such as the throat spot, should not be used as taxonomic characters, at least in the area where this study was conducted.

Seasonal Variation in the Body Size-Body Mass Relationship in the Southern Grey Shrike Lanius meridionalis

Abstract. n The variation of male (n = 105) and female (n = 107) Southern Grey Shrike body mass has been analyzed in northern Spain during 2000–2002. The annual cycle was divided into autumn (October and November), winter (December to February) and breeding season (March to July), the latter subdivided into egg incubation, small nestlings and large nestlings periods. In order to analyze body mass, the residual index (RI) was used because it corrects body mass related to body size. The mean RI value for males was negative during the whole breeding season and positive during autumn and winter and it did not vary greatly between the periods. In females, the mean RI was definitely greater during egg incubation compared to other periods. The RI value of females was higher than that of males during the egg incubation and large nestlings periods, showing no significant differences in other periods. Female Southern Grey Shrikes (but not males) fitted to the programmed anorexia hypothesis during the breeding season whereas in winter they did not increase their body mass, in clear contrast to what has been put forward in some theoretical models.