Yolk hormones have sex-specific long-term effects on behavior in the pied flycatcher (Ficedula hypoleuca)

The hormonal environment during early development, such as maternally derived androgens in bird eggs, shapes the development and phenotype of the offspring in ways that may have important long-term consequences for behaviour. We studied the effects of yolk androgens on multiple behavioural traits in female and male pied flycatchers (Ficedula hypoleuca) by experimentally elevating androgen levels (testosterone and androstenedione) in the eggs. The birds were housed in a common-garden environment in captivity until full independence, after which their behaviour was tested. We found that androgen-treated males were more likely than control males to explore a novel environment and showed higher activity in the presence of a novel object. In response to a simulated predator attack, androgen-treated males mainly showed freezing behaviour, while control males showed escape behaviour. Females from the androgen treatment and control group showed no differences in these behaviours. Androgen treatment did not affect neophobia (latency to approach the novel object) or dominance behaviour in either sex. Behaviour in the novel environment and towards a novel object was repeatable, but behaviours in the different experiments were mostly not inter-correlated. These results indicate that yolk androgens have various long-lasting effects on behaviour, especially in males, but that they do not induce a distinct behavioural syndrome. As behaviour is strongly linked with fitness, our results suggest that yolk androgens may play a role in determining fitness, and thus play a potentially adaptive role.     

Effects of long-acting testosterone treatment on freeliving pied flycatchers, Ficedula hypoleuca, during the breeding period

Breeding behaviour and spermatogenesis of all males in a population of pied flycatchers, Ficedula hypoleuca, were experimentally prolonged by long-acting testosterone. The behaviour of these birds was compared with that of birds from an untreated population and a population where the males were given the vehicle only. The testosterone treatment prolonged territorial behaviour, and a higher percentage of nests without a feeding male during the nestling period was found in the experimental area. The proportion of polygamous males did not however differ between the experimental and control areas. The feeding activity of those testosterone-treated males returning to their home territories was markedly depressed. The female of such a pair did not compensate for the male's low feeding activity, but fed the nestlings as she would have done with a normal untreated male at the nest. On the other hand, females without a male present during the nestling period compensated for their mates' absence by increasing their own feeding frequency. It was also shown that the song of the male pied flycatcher is dependent upon androgens. The testosterone-treated males produced fewer fledglings than the control males.     

Male polyterritoriality and imperfect female choice in the pied flycatcher, Ficedula hypoleuca

Polyterritoriality, the occupation of two spatially separateterritories by male birds, has been suggested to enable malesto conceal their pairing status. The idea that males deceivefemales has recently been questioned with arguments that femaleswould easily be able to detect polyterritorial males and thatthey mate in the second territories because better breedingoptions are not available close by. We arranged for pied flycatcher(ficedula hypoleuca) females a choice between neighboring unmatedand already-mated males. Females were unable to discriminateagainst already-mated males, even though their breeding successthereby would have been increased. These results allow rejectionof any polygyny models that assume females use male pairingstatus as a criterion for mate choice. Females would reducethe probability of mating polygynously by choosing dull, yearlingmales with high song rate, even though in most cases it is difficultto differentiate already-mated and unmated males. In fact, femalesdid not prefer colorful males, opposing a general pattern foundin other bird species. However, females did not specificallyprefer dull males nor did they respond to slight differencesin song rates. The seemingly nonadaptive, imperfect female behaviorsuggests that the evolution of female selectivity is constrained,allowing deception by males to be successful in the evolutionary‘arms race’ between the sexes. [Behav Ecol 1990,-1:171–177]     

Female aggressiveness towards female decoys decreases with mate T level in the pied flycatcher

Social selection is expected to favour the evolution of female aggressive defence of nesting resources in cavity-nesting birds, which may be also mediated by testosterone (T) levels. Male T levels could express male dominance and thereby territorial safety for female partners and thereby reduce their need for aggressive defence. Here, we explored the role of T levels in female-female competition in a songbird, the pied flycatcher Ficedula hypoleuca. In an experiment with female decoys placed close to the nestbox at the end of laying, we explored if female aggressiveness is related to their own T level or to mate T level. T levels of males and females were measured in the middle of the nestling period. Mean female aggressiveness towards decoys in three presentations was estimated through proximity to the decoy and number of attacks by females, two variables which were positively associated. Aggressiveness by female nest owners to female decoys was negatively related to male T level but unrelated to own T level. There was no assortative mating with respect to T level. Female aggressiveness is more strongly related to the hormonal status of mates than to their own.     

Ultraviolet dermal reflexion and mate choice in the guppy, Poecilia reticulata

Some fish, including the guppy, have the ability to perceive ultraviolet (UV) wavelengths. Female guppies prefer to associate with males that are viewed under light conditions that include UV-A, in preference to conditions lacking these wavelengths. We used reflexion spectrophotometry to show that male guppies reflect UV light from both their structural (purple, green and white) and pigment (orange) colour patches and that males differ in the levels of UV light reflected. Varying components of UV may affect both the brightness and hue of particular colour patches. This may produce nonspectral colours that are visible to the guppy but that are outside human perception. We used video analysis to quantify male reflexion in the UV and visible wavebands. Male guppies with high and low UV reflexion, but similar human-visible coloration and area of coloration, were paired for use in mate choice experiments. Female guppies shown pairs of males differing in their levels of UV reflexion had no preference for either high or low UV reflexion. This suggests that UV reflexion does not provide particularly significant information relating to male quality or influence female preference in this population of guppies. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour      

Ectoparasites,nest site choice and breeding success in the pied flycatcher

It has recently been suggested that nest box studies might bias the measurement of behavioural and life-history traits, because the removal of old nests may reduce the load of ectoparasites. This experimental artefact may have notable effects on nest site choice and breeding success in cavity-breeding birds. We tested (i) if pied flycatchers Ficedula hypoleuca prefer clean nest boxes and (ii) if old nest material affects the number of parasites and the breeding success of pied flycatchers. In the first experiment we offered birds one cleaned nest box and one nest box with old nest material from the previous year. The two nest boxes were placed in very similar sites near each other. In this experiment all pied flycatchers clearly preferred dirty nest boxes. In the second part of the study we distributed clean nest boxes and dirty ones on the same study area. After breeding was over we counted the number of fleas Ceratophyllus gallinae in the nest material. This flea species was the most abundant and probably the most hazardous parasite in the nests. Surprisingly, we found that there were significantly more fleas in the nest boxes with nests of the current year only than in the boxes with nests of both current and previous year. This might explain the preference for the dirty boxes. However, our results do not indicate that the number of fleas affects breeding success in the pied flycatcher.     

Pairing strategies and mate choice in female robins Erithacus rubecula

Female European robins (Erithacus rubecula) adopted three different pairing strategies. These were, in order of frequency: moving on to a male's territory; fusing her territory with that of a neighbouring male; and being joined by a male on her territory. Although females were not free to choose between strategies during a particular season, individuals frequently changed strategy between different years. Their behaviour suggested that they were exercising mate choice, although the scope for such choice was limited by a strong tendency for a female to pair in areas where she had lived previously (her ‘Familiar Areas’). Males with large territories were more likely to pair and tended to pair earlier than those defending small territories. Female pairing strategy was also correlated with the area of their own territory. Although it is considered likely that some unidentified confounding variable was responsible for at least part of these relationships, possible causal explanations involving territory size are discussed. These include mate choice and a random settlement model. However the simplest explanation for the advantage enjoyed by males on large territories is that their territories were more likely to overlap with females' Familiar Areas.     

Female mate choice in the pupfish, Cyprinodon variegatus

Experimental evidence suggests that female Cyprinodon variegatus do not select between competitively inferior and superior males, but rather, deposit eggs randomly and in proportion to the size of the male's territory. The females do seem to have an habitat preference and probably influence the location where males compete for territorial space.     

Evidence for differential maternal allocation to eggs in relation to manipulated male attractiveness in the pied flycatcher (Ficedula hypoleuca)

We present evidence of differential maternal allocation to eggs in response to manipulated male attractiveness in the migratory pied flycatcher (Ficedula hypoleuca). We manipulated the size of a male secondary sexual trait, the white forehead patch, right after male arrival to the breeding area and before female arrival. Patch size was (1) enlarged to the maximum observed in the population, (2) reduced by 40% or (3) kept constant by painting with indelible felt markers over the natural feather patch. Male behaviour was affected by the experimental manipulation, as individuals with enlarged patches performed more approaches to the nestbox in response to song playback during the territory occupation and nest-site presentation phases. Females paired with males with reduced forehead patches laid significantly smaller eggs than those paired with males in the control and enlarged-patch treatments. Laying date and clutch size did not differ among the experimental groups. We discuss that manipulations of ornaments designed to study differential allocation at laying should reduce as well as enlarge their expression.     

Effect of female brooding behaviour on male mate choice in Japanese quail, Coturnix japonica

Brooding behaviour is a likely cue to a female's reproductive status and therefore a potentially important factor in male mate assessment. We induced brooding behaviour in adult female Japanese quail by exposure to foster chicks for five 20-min trials over 3 days. In two experiments, we assessed the influence of this brooding behaviour on male mate choice in Japanese quail using an established mate choice paradigm. In each experiment we gave males a choice between two females presented simultaneously and measured preference by the time spent in proximity to each. In the first experiment, a male's preference for the initially preferred female significantly decreased after he had seen her brooding three chicks. In the control condition, male preference for an initially preferred female remained relatively consistent over consecutive trials if he did not see her brood chicks. These results suggest that females who are brooding chicks are less attractive to male Japanese quail. Further evidence from the second experiment substantiates this finding, and strongly suggests that males are averse to behavioural cues from maternal females, rather than the mere presence of chicks. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.      

Scent marking and mate choice in the prairie vole, Microtus ochrogaster

Scent marking is common among male and female rodents and might be used in male-male competition and as a mechanism for mate attraction. I tested the hypotheses that females would choose males based on their frequency and placement of scent marks, and that a female would advertise interest in a particular male by placing her scent marks on or near those of a preferred mating partner. In a series of experiments conducted with prairie voles, Microtus ochrogaster, females did not choose mates based on the frequency or placement of scent marks by males nor did they advertise their interest in a particular male through the frequency or placement of scent marks. The number of males chosen that scent-marked more than their opponents did not differ significantly between females exposed (11 of 15) and not exposed (10 of 15) to scents of males. Females exposed and not exposed to scents of males preferred seven of the same males that had scent-marked more than their opponents. When a third group of females was exposed to four times more scent of the less preferred than preferred males, they still chose the preferred males. Thus, the frequency and placement of scent marks by males were not used to assess males for mate choice nor did female prairie voles use scent to advertise their preference for a mating partner. In that scent marking is common in male and female mammals, scent quality might be more important than quantity in male-male competition and mate attraction.Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved .