Emilio Pagani-Núñez

One Hour of Sampling is Enough: Great Tit Parus major Parents Feed Their Nestlings Consistently Across Time

Abstract. Parental investment is a key topic in avian ecology, and many authors have focused on nestling-feeding behaviour to analyse this issue. Surprisingly, most studies have based their results on feeding patterns recorded over periods of only one or two hours, possibly leading to over generalizations regarding temporal-dependent behavioural patterns. Irrespective of nestling age or brood size, if we use observations from such short periods as conclusive evidence we must assume that parents behave consistently across time and that the window of time selected is representative of parental effort. To test this assumption, we analysed the time consistency of nestling provisioning rates and prey composition of 32 breeding pairs of Mediterranean Great Tits Parus major, from dawn to midday (7 hours recording). Regardless of a parallel decrease in the intensity of work for both sexes, we found that hourly provisioning rates per nestling correlated strongly with the mean number of feedings per nestling and per hour recorded over the whole 7 hours of recording. Weather conditions and nestling age had no effect on hourly provisioning rates per nestling, although parents with older nestlings worked relatively less hard. We also observed that the peak of morning activity was higher in nests with small clutches. Prey proportions showed a high degree of temporal repeatability, but nestling diet composition should be studied with caution. Although prey composition was stable over time, we recorded a strong decrease in the number of prey items delivered by parents throughout the day, along with an increase in prey size. We thus recommend using a wider time window to obtain reliable results when studying prey composition. In any case, considering our results, one hour of recording may be sufficient to describe nestling-feeding behaviour of Great Tit parents.

Year-Round Preference for Spiders by Mediterranean Great Tits Parus major

Summary. A key topic in foraging ecology is whether a particular prey type is consumed because it is more abundant or easier to catch, or because there is a specific preference for it. The great tit Parus major is an ideal species for studying this topic. Although it is traditionally regarded as a caterpillar specialist, in certain periods, e.g. during the breeding season, or areas, such as the Mediterranean forests, the great tit seems to show a preference for spiders. We conducted food choice experiments with captive birds to ascertain which of these two main prey types (caterpillars vs. spiders) was preferred outside the breeding season when there was an opportunity to prey on both food types. In conclusion, we found that, regardless of any variation in the supply-demand ratio and the amount of food available, Mediterranean great tits showed a preference for spiders.

More Ornamented Great Tit Parus major Fathers Start Feeding Their Offspring Earlier

Carotenoid-based ornaments have been proposed to signal the ability to find food. The good-parent hypothesis suggests that females may rely on these carotenoid-based traits to assess male parental quality. A key question is whether the quality of these ornaments correlates with their performance at the moment of breeding. In this study, we assessed the parental investment of Mediterranean Great Tits Parus major in the early morning as a function of several environmental factors and of parental ornamentation. We measured this by the time that parents started feeding their offspring at the start of the day. In the morning, parents need to rapidly respond to the food demands of their offspring, after a long night without food. An earlier start of provisioning could indicate higher parental investment (and/or greater foraging ability). Our data indicate that fathers that show higher hue in their carotenoid-based plumage — more greenish individuals — started feeding their offspring earlier, thereby expanding the time window in which they work, while females did not show a significant relationship between the onset of provisioning and ornamentation. Parents, particularly mothers, that started earlier, worked more intensely across the whole observation period. Furthermore, parents started earlier when they had larger broods. Finally, more ornamented parents worked at lower rates, while more ornamented mothers raised offspring that had better body condition, which is in line with the good parent hypothesis. Although our results indicate that more ornamented males start feeding their offspring earlier, overall we found mixed support for the hypothesis that carotenoid-based ornaments signal the parental quality of a mate.

Wintering location and moult patterns of juvenile Common Chiffchaffs Phylloscopus collybita

Capsule The pattern of moult of juvenile Common Chiffchaffs Phylloscopus collybita wintering in two distant localities of the Iberian Peninsula, Málaga (south) and Barcelona (north) differed. Individuals wintering in the northern locality moulted more contour than flight feathers, and vice versa, while sexes did not differ; individuals moulting more contour feathers arrived later and individuals moulting more flight feathers arrived earlier. Taken together, our results suggest that the pattern of moult of juvenile Common Chiffchaffs may depend on the location to which they migrate, in addition to the geographic origin and the time of breeding.

Red-billed Leiothrix sexing is a matter of colour

Capsule The Red-billed Leiothrix (Leiothrix lutea) is a superficially sexually monochromatic colourful bird native to the Indian subcontinent, which has colonized many locations across the world as an introduced species. We investigated the best method to accurately sex the species, capturing and measuring the colour and external morphometry of a sample of 57 individuals, which were later sexed molecularly from blood samples. We found that sexes showed no dimorphism in biometry or size of wing coloured-patches. However, a Discriminant Function based on hue of the throat, chroma of the crown and lightness of the breast allowed us to determine sex with an accuracy of 91%.