Gábor Michl

Experimental analysis of sperm competition mechanisms in a wild bird population

Recent work on wild birds has revealed the importance of sperm competition as a source of sexual selection, but behavioral and paternity studies have previously provided only indirect evidence for mechanisms of sperm competition in wild birds. In a field study of collared flycatchers Ficedula albicollis we used a previously uncharacterized method to determine the frequency and timing of extra-pair inseminations. By counting the number of sperm trapped on the perivitelline layer of eggs, we determined the timing of inseminations and estimated, on a day-to-day basis, the amount of sperm females stored. Our results showed that female collared flycatchers preferentially engaged in extra-pair copulations when mated to an unattractive male with a small white forehead patch. These copulations were timed for the middle part of their fertile period, at least 2 days after the last within-pair insemination. Although the mean number of extra-pair insemination events was only 1.33 per cuckolding female, the ratio between the number of sperm from extra-pair and pair inseminations was at least 5 to 1. Thus a single, well timed extra-pair insemination caused by female behavior could greatly bias fertilization probability in favor of an attractive extra-pair male. Our results suggest a possible behavioral mechanism for female control of sperm competition.

Carotenoids in the egg yolks of collared flycatchers (Ficedula albicollis) in relation to parental quality, environmental factors and laying order

Birds may influence the fitness of their offspring by transmission of different amounts of carotenoids to their eggs. Carotenoids play crucial roles in antioxidant protection and immune defence mechanisms, but they may be available to females in limiting amounts. Therefore, their allocation to the eggs may be influenced by the female’s condition, age and environmental circumstances. Furthermore, the quality of the male parent, which affects the reproductive value of the offspring, may also influence this investment. In this correlational study, we investigated proximate and ultimate factors that may lead to variation in yolk lutein, zeaxanthin and β-carotene concentrations among and within clutches of a wild passerine, the collared flycatcher (Ficedula albicollis). We found that carotenoid concentration was positively associated with caterpillar supply at the time of egg formation, which suggests a proximate constraint of carotenoid availability on yolk composition. Neither female condition, body size, age, nor male plumage ornamentation, age and body size correlated with carotenoid deposition. Yolk β-carotene concentration was found to be positively linked to yolk testosterone concentration. We suggest that females allocated more β-carotene to their eggs to mitigate the potentially detrimental effects of elevated steroid concentration. We found that concentration of β-carotene increased with laying order. The possible function of this pattern may be to enhance the resistance to oxidative stress and pathogens of the disadvantaged last-hatching nestling, suggesting that collared flycatchers pursue a compensatory, “brood survival” strategy.

Oxidative damage and plasma antioxidant capacity in relation to body size, age, male sexual traits and female reproductive performance in the collared flycatcher (Ficedula albicollis)

The study of oxidative stress is a potential tool for studying the functional interactions among life history traits, sexual traits and physiological status in animals. In this study, we investigated relationships between measures of plasma oxidative status and male sexual traits, female reproductive investment and three other life history traits, in a wild population of collared flycatchers (Ficedula albicollis). Flycatcher males with a larger white forehead patch had higher level of plasma antioxidant capacity. For females, clutch size was not associated with plasma oxidative status, but egg size was positively correlated with antioxidant capacity. The relationship between age and levels of plasma oxidative damage remains controversial in this species: young female flycatchers showed higher levels of hydroperoxides compared to antioxidants, whereas age did not predict oxidative status of males. Males had higher levels of oxidative damage than females, although the concentration of antioxidant compounds was similar between the sexes. Females that mated with more ornamented males had higher plasma antioxidant capacity. Our results suggest that, for males and females, greater investment in sexual signal and reproduction, respectively, does not reduce the capacity for self-maintenance or avoidance of oxidative stress. Finally, our data support indirectly the occurrence of assortative mating in our species, since females with higher plasma antioxidant capacity mated with more ornamented males.

Common cuckoos (Cuculus canorus) lay eggs with larger yolk but not more testosterone than their great reed warbler (Acrocephalus arundinaceus) hosts

The relatively small common cuckoo Cuculus canorus hatchling evicts its hosts propagules, then begs intensively to elicit sufficient parental care. The proximate mechanisms of these behaviours are still obscure. Recent intraspecific studies on avian broods revealed higher competitive ability of nestlings that hatched from eggs with a greater yolk testosterone level. Greater maternal investment in yolk steroids may provide an explanation for the vigour of parasitic chicks. Unexpectedly we found no evidence of higher yolk T concentration and absolute amount of T in cuckoo eggs compared to those of its host, the great reed warbler Acrocephalus arundinaceus. The yolk mass of cuckoo eggs, however, was significantly greater than that of the host, despite egg volumes being similar between these two species. Relatively larger yolks of cuckoo eggs indicates differential maternal investment strategies by parasites as more yolk may contain additional macronutrients to increase the vigour of parasitic young during the early days of its life and/or to enhance its begging display to elicit care from foster parents.

The estimation of size and change in composition of avian song repertoires

*Laboratoire d’Ecologie Evolutive Parasitaire CNRS UMR 7103, Universite´ Pierre et Marie Curie†Behavioral Ecology Group, Department of Systematic Zoology and Ecology, Eo¨tvo¨s Lora´nd University, Hungary‡Laboratoire d’Ecologie, CNRS UMR 7625, Universite´ Pierre et Marie Curie§U.S. Geological Survey, Biological Resources Division, Patuxent Wildlife Research Center, U.S.A.

Effect of timing and female quality on clutch size in the Collared Flycatcher Ficedula albicollis

Capsule Laying date and female age appear to be related to clutch size. Aims To test two hypotheses (‘date’ and ‘quality’), which might explain why fewer eggs are laid late in the season. Methods Four years of data and multivariate analysis were used to test the effects of timing of breeding and female quality reflected by morphological variables and age on clutch size in the Collared Flycatcher Ficedula albicollis. We estimated food supply during parental care by measuring diet composition of nestlings. Results We distinguished the independent effects of date and age of females on clutch size. The type of prey fed to nestlings was different early and late in the season. Hence food supply during the nestling care period may be a limiting environmental factor that indirectly determines clutch size. Conclusion Our results are consistent with the predictions of the date hypothesis, but the quality hypothesis was also partially supported. Depending on year effects, 30–50% of the variance in clutch size may be related to the timing of breeding and an additional 5–10% may be due to quality (age) differences between early- and late-breeding birds.

Repeated inseminations required for natural fertility in a wild bird population

In most bird species, pairs copulate many times before egg laying. The exact function of repeated inseminations (i.e. successful copulations) is unknown, but several suggestions have been made. We tested the hypothesis that repeated inseminations are required to ensure fertilization of eggs, by using an experimental method where free–ranging male collared flycatchers (Ficedula albicollis) were prevented from inseminating their mates. We show that egg fertility was lower when females had not copulated during the studied part of their fertile period. By counting sperm on the inner perivitelline layer of eggs, we estimated that a minimum of 86 sperm must reach the site of fertilization to ensure average fertility. Using the timing of inseminations and the numbers of sperm on successive eggs, we show that repeated copulations are necessary to achieve an average rate of fertilization of a single clutch. Our results thus provide evidence that repeated inseminations function to ensure fertilization success. We discuss possible constraints on sperm production and utilization that may have contributed to this pattern.

Distribution and phenological data of some bird species of Uganda

Abstract During a twenty five days trip in Uganda a brief faunistic survey of birds, mammals and reptiles was performed. Altogether 380 bird species were observed in six National Parks and some other protected areas in the summer of 2012. From these 64 bird species are discussed here selected according the following criteria: rarity, occurrence in a new habitat or geographic area, and emergence of novel breeding phenological data of certain species. Our new records of House Sparrow (Passer domesticus) along the Kazinga Channel (between Lake Edward and Lake George) are outside the current distribution range of the species. The House sparrow expanded its area about 800 km toward west from their first record in Nairobi in 1992. Our new records on White-tailed Ant-thrush (Neocossyphus poensis), Red-tailed Ant-thrush (Neocossyphus rufus), Papyrus Yellow Warbler (Chloropeta gracilirostris), Shelley’s Rufous Sparrow (Passer shelley) and Streaky Seedeater (Serinus striolatus) also require the correction of distribution maps of this species in Uganda. In addition we give some remarks on the breeding phenology of Mountain Wagtail (Motacilla clara), Cassin’s Grey Flycatcher (Muscicapa cassini) and Northern Red Bishop (Euplectes franciscanus). Our recent observational data of African Skimmer (Rynchops flavirostris) may have importance for the Bonn Convention. These observations might be important from conservation and ecotouristic point of views Összefoglalás 2012. július 11. és augusztus 4.-e között 25 napot töltöttünk el Ugandában madarak, hüllők és emlősök megfigyelésével. Utunk során hat nemzeti parkot és számos egyéb védett területet kerestünk fel, összesen 380 madárfajt észleltünk. Közülük 64 fajt válogattunk ki, melyek előfordulási és viselkedési adatainak közzététele érdeklődésre tarthat számot különféle szempontok, mint a természetvédelem, ökoturizmus, költésbiológia alapján, vagy az elterjedési területük változása miatt. A házi veréb (Passer domesticus) kelet-afrikai terjeszkedése során mintegy 10 éve érte el Ugandát, ezért a Kazinga-csatorna melletti megfigyelés jelentős új adatnak számít. További új előfordulási adatok a fehérfarkú hangyarigó (Neocossyphus poensis), a vörösfarkú hangyarigó (Neocossyphus rufus), a papirusz poszáta (Chloropeta gracilirostris), a nílusi veréb (Passer shelley), a csíkos csicsörke (Serinus striolatus) vonatkozásában születtek. Költésbiológiai adatokat közlünk a pataki billegető (Motacilla clara), a cassin-légykapó (Muscicapa cassini) és a tűzhátú szövőmadár (Euplectes franciscanus) vonatkozásában. A részleges vonuló afrikai ollóscsőrűmadár (Rynchops flavirostris) előfordulási adata érdekes lehet a Bonni Egyezmény szempontjából