Ringing

En muchas especies es imposible distinguir visualmente los sexos, si bien en algunas de
ellas, machos y hembras muestran pequeñas, pero cuantificables, diferencias  biométricas que pueden usarse para discriminarlos. Este es el caso del grupo de los mosquiteros Phylloscopus, en los que se usa la longitud alar para distinguir los sexos. Hemos desarrollado un método en el que además del ala se tiene en cuenta el tarso y en el que mediante probabilidades multivariantes hemos aumentado la proporción de individuos que se pueden discriminar en tres especies: mosquitero común P. collybita, mosquitero musical P. trochilus y mosquitero ibérico P. ibericus. Además, nuestro método de sexado no tiene sesgos hacia uno de los dos sexos. El objetivo de este artículo es ofrecer una guía práctica para la implementación de nuestro método usando el software libre R.

This is the 74th annual report of the British Trust for Ornithology's Ringing Scheme, covering data received and work carried out in 2010. Analytical work in the year concentrated on considering how we can improve demographic monitoring, an increasing focus for the Scheme. A broad review of the availability of demographic and count data for terrestrial-breeding species was carried out. This work will be further extended in 2011. To inform conservation we need to build population models for species with a range of ecologies and occupying different habitats. Reports of ringed birds make a large contribution to our understanding of two key demographic parameters – survival and dispersal. An analysis of Chiffchaff Phylloscopus collybita recovery data from across Europe suggested they are tending to migrate south later and north earlier over time. There is also a suggestion that the migratory journey is shortening. Analysis of biometrics of birds wintering in Britain showed that they are largely from the breeding populations of the nominate race in Britain and the near Continent. Constant Effort Sites (CES) data showed that, for seven of the 24 species monitored, there was a significant decrease in adult abundance compared to the mean of the previous five years. As six of these species were residents, this may have been a result of the second severe winter in succession, although there was a short-term increase for Long-tailed Tit Aegithalos caudatus, which is usually affected by cold winters. The adult abundance of several long-distance migrants also increased. A long-term decline (1984–2000) is, however, still evident for five migrants and three residents, although for Willow Tit Poecile montana and Linnet Carduelis cannabina the sample sizes are low. The abundance of the short-distance migrants, Blackcap Sylvia atricapilla and Chiffchaff, has increased, possibly as a result of climate change. Productivity was higher than the mean of the previous five years for 12 species with the long-term trend increasing for eight species – four migrants and four residents. The only significant decreases were for Blackbird Turdus merula and Long-tailed Tit, possibly as these species breed early and were affected by the severe winter. Dry summer weather is also likely to have contributed to the low productivity of Blackbirds and increasingly dry summers may be implicated in the long-term declines in productivity for both Blackbird and Song Thrush Turdus philomelos. Long-term trends in survival rates were produced using CES data for the first time in 2010. These suggested that the cold winter weather in 2009–10 reduced the survival rate of resident ground-feeding insectivores such as Dunnock Prunella modularis, Blackbird, Wren Troglodytes troglodytes and Robin Erithacus rubecula. Survival rates of migrants were relatively high, particularly for Garden Warbler Sylvia borin and Sedge Warbler Acrocephalus schoenobaenus, possibly as a result of good conditions on the wintering grounds or passage sites. Data for 129 Retrapping Adults for Survival (RAS) studies covering 39 species were submitted. For the first time we were able to calculate good or moderate annual estimates of survival for 18 species. A list of priority species for RAS was developed and promoted to volunteers. The total number of birds ringed (1,096,533) was the highest ever recorded, as well as being the first time the annual total has surpassed 1 million. It was 28% higher than the mean of the previous five years and 17% higher than in 2009. However, the total number of pulli ringed in 2009 (193,554) was only 12% higher than the preceding five-year mean, while that of fully grown birds (902,979) was 32% higher. The recovery total (17,315) was also the highest ever. This is partly due to changes in the way that records of colour-ringed and other specially marked birds are stored, but also reflects the increasing number of birds being ringed by a growing number of ringers. The number of recoveries of foreign-ringed birds (2,427) was higher than the mean of the preceding five years; this figure was influenced by varying response times of different ringing schemes, but was also partly as a result of multiple sightings. Recovery details for 221 individual birds are given in the final section of the report. They include movements that confirm suspected or known migration patterns, unexpected movements and longevity records.

The Iberian Chiffchaff Phylloscopus ibericus has recently been accepted as a full
species, but is still very difficult to distinguish from the Common Chiffchaff P. collybita when molecular
and acoustic evidence is lacking. Distinguishing these cryptospecies is essential for obtaining accurate
population estimates for each, which is especially important in the case of the Iberian Chiffchaff due
to its restricted distribution. We re-assessed the discriminant methods available in the literature and
propose some alternative traits to distinguish both species. We used information from 24 morphological
traits measured in c. 6,700 individuals of the two species trapped during the autumn migration period
in Doñana National Park, Spain, between 2004 and 2015. Discriminatory methods available in the
literature were unable to distinguish the two species efficiently. Despite some biometric differences,
morphological measurements showed a high degree of overlap and so could not distinguish between
Iberian and Common Chiffchaffs. The best discriminatory factor at our study site was the passage date,
since 90% of Iberian Chiffchaffs have already departed when the first Common Chiffchaffs arrive. Those
traits associated with migration, such as wing size and shape and fat deposits, were also able to
discriminate the species, albeit weakly. This result fully concurs with the trans-Saharan migration of
the Iberian Chiffchaff in contrast to the Common Chiffchaff, which chiefly winters in Mediterranean
latitudes. In conclusion, biometric traits are useless for discriminating the two species and we do not
recommend their use. A comprehensive examination of colouration and plumage seems to be the only
reliable way of guaranteeing the correct identification of these species in the hand.

Key words: autumn migration, cryptic species, discriminant analysis, identification, morphology,
Phylloscopus.

In this paper we classified the sex of 39 Iberian Water Rails Rallus aquaticus using external morphometric measurements and genetic analysis. Logistic regression and classification tree model techniques (CART) were used to test whether simple morphometric measurements alone could classify sex correctly. For most of these measurements the overlap between sexes was too great to be of value. Bill length was the most relevant variable according to all the statistical analyses for the population under study. The applied combination of statistical techniques on biometric and genetic data correctly classify 80% of individuals. However, in view of the apparent variability in morphometric characteristics between populations, morphometric techniques to sex individuals from other populations should be validated using other criteria.

Based on variations in breast plumage colour, two subspecies of White‐throated Dipper Cinclus cinclus have been acknowledged to exist in Spain: C. c. cinclus in northwestern and central regions, and C. c. aquaticus in the eastern and southern regions. Within the White‐throated Dipper's Spanish range, 37 rivers were sampled between 2000 and 2007. Dippers with a brownish‐red and dark brown breast plumage were both present within the same large areas and rivers. Moreover, because plumage colour changes individually with age, no clear‐cut geographical distribution pattern was found. These observations suggest that breast colour cannot be used to distinguish White‐throated Dipper subspecies in Spain.

State-space models have recently been proposed as a convenient and flexible framework for specifying stochastic models for the dynamics of wild animal populations. Here we focus on the modelling of data on marked individuals which is frequently used in order to estimate demographic parameters while accounting for imperfect detectability. We show how usual models to deal with capture–recapture and ring-recovery

Recently, the use of ground-penetrating radar (GPR) arrays with a large number of antenna elements in a fixed configuration has become more common. The investment needed for these systems is significant. Although gradually expandable modular systems, consisting of antennas which can be used independently, do not match the fast acquisition of detailed datasets by means of multi-channel arrays, they can help finding a compromise between increased acquisition speed and (limited) resources. In modular systems, the separation between transmitter-receiver pairs is often larger than the sampling distance prescribed by the Nyquist theorem. As a consequence, additional profiles have to be recorded in between, which requires a high positioning precision. As a completely identical response for the different antennas in an array is difficult to achieve, stripes can occur in the horizontal slices, especially when ringing occurs. This complicates the interpretation of features in the direction of the survey lines. In this paper, a three dimensional frequency-wavenumber filter is proposed, consisting in a combination of a circular filter and a fan filter. The application of this filter to GPR data collected at the Roman town Mariana (Corsica, France) showed a reduction of the stripe patterns, allowing a more reliable characterization of subtle archaeological structures.