Difficulties when Assessing Birdsong Learning Programmes under Field Conditions: A Re-Evaluation of Song Repertoire Flexibility in the Great Tit

There is a remarkable diversity of song-learning strategies in songbirds. Establishing whether a species is closed- or open-ended is important to be able to interpret functional and evolutionary consequences of variation in repertoire size. Most of our knowledge regarding the timing of vocal learning is based on laboratory studies, despite the fact that these may not always replicate the complex ecological and social interactions experienced by birds in the wild. Given that field studies cannot provide the experimental control of laboratory studies, it may not be surprising that species such as the great tit that were initially assumed to be closed-ended learners have later been suggested to be open-ended learners. By using an established colour-ringed population, by following a standardized recording protocol, and by taking into account the species' song ecology (using only recordings obtained during peak of singing at dawn), we replicated two previous studies to assess song repertoire learning and flexibility in adult wild great tits elicited by social interactions. First, we performed a playback experiment to test repertoire plasticity elicited by novel versus own songs. Additionally, in a longitudinal study, we followed 30 males in two consecutive years and analysed whether new neighbours influenced any change in the repertoire. Contrary to the previous studies, song repertoire size and composition were found to be highly repeatable both between years and after confrontation with a novel song. Our results suggest that great tits are closed-ended learners and that their song repertoire probably does not change during adulthood. Methodological differences that may have led to an underestimation of the repertoires or population differences may explain the discrepancy in results with previous studies. We argue that a rigorous and standardized assessment of the repertoire is essential when studying age- or playback-induced changes in repertoire size and composition under field conditions

Estrogen and Progestogen Correlates of the Structure of Female Copulation Calls in Semi-Free-Ranging Barbary Macaques (Macaca sylvanus)

Females of many Old World primates produce conspicuous vocalizations in combination with copulations. Indirect evidence exists that in Barbary macaques (Macaca sylvanus), the structure of these copulation calls is related to changes in reproductive hormone levels. However, the structure of these calls does not vary significantly around the timing of ovulation when estrogen and progestogen levels show marked changes. We here aimed to clarify this paradox by investigating how the steroid hormones estrogen and progesterone are related to changes in the acoustic structure of copulation calls. We collected data on semi-free-ranging Barbary macaques in Gibraltar and at La Forêt des Singes in Rocamadour, France. We determined estrogen and progestogen concentrations from fecal samples and combined them with a fine-grained structural analysis of female copulation calls (N = 775 calls of 11 females). Our analysis indicates a time lag of 3 d between changes in fecal hormone levels, adjusted for the excretion lag time, and in the acoustic structure of copulation calls. Specifically, we found that estrogen increased the duration and frequency of the calls, whereas progestogen had an antagonistic effect. Importantly, however, variation in acoustic variables did not track short-term changes such as the peak in estrogen occurring around the timing of ovulation. Taken together, our results help to explain why female Barbary macaque copulation calls are related to changes in hormone levels but fail to indicate the fertile phase

Calculations of provincial environmental costs with RIM+. A pilot study for Limburg

De resultaten werden beschreven van een haalbaarheidsstudie met als doel om na te gaan of het RIM+ (Reken en informatiesysteem Milieuhygiene) dat nu door het RIVM wordt gebruikt voor het doorrekenen van nationale milieukosten, ook geschikt is voor het maken van provinciale milieukostenberekeningen. Hiertoe zijn voor een provincie (Limburg) de benodigde gegevens verzameld en ingevoerd in RIM+, waarna milieukosten met RIM+ zijn berekend. Resultaat van de pilot is dat het inderdaad mogelijk is provinciale milieukosten te berekenen met het RIM+. De uitkomsten zijn wat methodiek, soort resultaten en kwaliteit betreft vergelijkbaar met de kostenberekeningen die TME in 1994 voor de provincies heeft uitgevoerd. Tijdens de pilot is een aantal knelpunten onderkend, waarmee in een eventuele vervolgfase rekening moet worden gehouden. Behalve met het model RIM+ hebben deze knelpunten betrekking op de organisatie van provinciale kostenberekeningen en de methodiek en databehoefte van een provinciaal kostenmodel. Drie opties voor een provinciaal milieukostenmodel worden geevalueerd. Uiteindelijk wordt een voorstel gepresenteerd, dat zoveel mogelijk de positieve punten van de verschillende opties combineert.As a first step in the cooperation between provinces and RIVM in developing a model for calculations of environmental costs, a pilot study was carried out to calculate the environmental costs to the Dutch province of Limburg using the model RIM+. This model, already used by RIVM for calculations of environmental costs on a national level, had to be partly adapted. The pilot shows that it is indeed possible to use RIM+ for provincial cost calculations. In carrying out the pilot, insight was gained into detailed desires and requirements related to input, output, methods and organisational aspects. Based on the results three options for the future are evaluated, in an advice for future actions.provincie LimburgDG

Intra- and interspecific relationships between nest size and immunity

Nest-building behavior has been suggested to represent a postmating sexually selected signal in passerine birds, an hypothesis that has received both comparative and experimental support. Because selection pressure due to parasites and diseases should be particularly high during nest building, mainly due to energetic costs and depression of the immune system associated with this reproductive phase, we predicted a positive association between nest-building effort and immunity. Nest-building effort would reflect the ability to produce efficient immune responses of builders only if individuals with a superior immune system would display exaggerated nest-building effort. We tested this prediction by studying the relationship between volume of nest material used for nest construction and, at the intraspecific level, estimates of innate humoral immune response in barn swallows Hirundo rustica. At the interspecific level, we used responses to the mitogenic phytohemagglutinin as an indicator of adaptive immune response of European passerine species. As predicted, we found, after controlling for several potential confounding factors, that volume of nest material was positively related to immune response both at the intra- and at the interspecific level. Alternative hypotheses explaining the comparative results are discussed. Copyright 2007, Oxford University Press.