Is Mate Provisioning Predicted by Ornamentation? A Test with Northern Cardinals (Cardinalis cardinalis)

Male birds of many species feed their mates during courtship and incubation. The amount of food provided can be substantial and even essential for successful reproduction in some species, and can influence female nest attentiveness in many others. Additionally, mate provisioning may predict later nestling feeding rates. Females may thus benefit from being able to determine male provisioning effort. We assessed the expression of several ornaments, known to indicate condition in male northern cardinals (Cardinalis cardinalis), and compared these with mate provisioning rates, nestling feeding rates, and nest attentiveness. We found that male ornamentation may not be indicative of mate provisioning rates. Mate provisioning rate did not co‐vary with reproductive success, male feedings to nestlings, or nest attentiveness of females. However, females which were fed more often during incubation tended to provision nestlings less. Reduced female parental effort following extensive incubation feeding may be indicative of females using incubation feeding to assess future male parental effort. Male hormonal condition that favors high rates of nestling provisioning may be a proximate cause of mate provisioning during incubation, even in the absence of selection, favoring high rates of mate provisioning. Both sexes may have capitalized on this unselected behavior.     

Handicapped females receive more feedings during incubation from their mates: support for the female nutrition hypothesis

The female nutrition hypothesis posits that provisioning intensity of incubating females by their mates may depend on female needs and ensure proper incubation and a corresponding high hatching and breeding success of breeding pairs. Here, we have handicapped female pied flycatchers Ficedula hypoleuca at the beginning of incubation by clipping two primaries on each wing and filmed nests during incubation and later nestling provisioning to estimate male involvement in incubation feeding at the nest and in offspring care. Incubation feeding was more frequent at late nests. Correcting for this seasonal effect, incubation feeding was significantly affected by treatment and twice as high at experimental as at control nests. There was no effect of the experiment on female incubation attendance. The handicap did not result in any effect on hatching and breeding success, nestling growth and male or female provisioning and mass at the end of the nestling period. Males adjust their incubation feeding activity at the nest to female energetic requirements during incubation.     

Selective Prey Delivery to Incubating Females by Dominant Males, but not Helpers, in the Cooperatively Breeding Green Woodhoopoe

In cooperatively breeding bird species, one of the most conspicuous helping behaviours is the provisioning of food. Many studies have considered the feeding of nestlings, but far fewer have examined feeding of incubating females, and none have looked at the types of prey delivered at this stage. Here I show that green woodhoopoe ( Phoeniculus purpureus ) group members selectively feed incubating females with certain prey items: the diet delivered to incubating females contains a higher proportion of caterpillars, centipedes and cockroaches than that eaten by the provisioning adults themselves. The prey items selectively delivered are the largest in the diet and so might be provided in an effort to enhance the breeding female's condition, thus minimizing the time that she spends off the nest and so increasing hatching success. Intriguingly, it is only breeding males that show this adjustment in provisioning diet; helpers of both sexes simply provide the incubating female with the same proportions of different prey items that they eat when self-feeding. My results therefore offer the first evidence that members of cooperative groups may not all follow the same provisioning rules, and they also emphasize the need for studies to consider the incubation stage in just as much detail as the nestling phase if we are to understand fully the complexities of cooperative societies.     

Incubation Feeding and Nest Attentiveness in a Socially Monogamous Songbird: Role of Feather Colouration,Territory Quality and Ambient Environment

Parental investment and environmental conditions determine reproductive success in wild‐ranging animals. Parental effort during incubation, and consequently factors driving it, has profound consequences for reproductive success in birds. The female nutrition hypothesis states that high male feeding enables the incubating female to spend more time on eggs, which can lead to higher hatching success. Moreover, both male and female parental investment during incubation might be signalled by plumage colouration. To test these hypotheses, we investigated relationships between male and female incubation behaviour and carotenoid and melanin‐based plumage colouration, territory quality and ambient temperature in the Great Tit Parus major. We also studied the effect of female incubation behaviour on hatching success. Intensity of male incubation feeding increased with lower temperatures and was higher in territories with more food supply, but only in poor years with low overall food supply. Female nest attentiveness increased with lower temperatures. Plumage colouration did not predict incubation behaviour of either parent. Thus, incubation behaviour of both parents was related mainly to environmental conditions. Moreover, there was no relationship between male incubation feeding, female nest attentiveness and hatching success. Consequently, our data were not consistent with the female nutrition hypothesis.     

Paternal care as a conditional strategy: distinct reproductive tactics associated with elaboration of plumage ornamentation in the house finch

When individuals in a population differ in physiological conditionand residual reproductive value, selection should favor phenotypicplasticity in reproductive investment such that individualsare able to adopt the reproductive tactic that results in thehighest fitness under given conditions. Here we examined reproductivetactics in relation to the elaboration of condition-dependentsexual ornamentation (carotenoid breast coloration) in a Montanapopulation of the house finches (Carpodacus mexicanus). Malesused distinct reproductive tactics depending on elaborationof their sexual ornamentation. Males with red pigmentation (maximum ornament elaboration) paired with females that nestedearlier, but these males did little provisioning of incubatingfemales and nestlings. In contrast, males with yellow colorationpaired with females that nested later, but these males fedfemale and nestlings more. Consequently, for red males offspringrecruitment was primarily affected by earlier nest initiation, whereas in yellow males it was affected most by male provisioning.In males with intermediate plumage coloration, all measuredcomponents, nest initiation, provisioning of incubating female,and nestling feeding, strongly contributed to offspring recruitment.The fitness consequences of alternative reproductive tacticsof males were influenced by breeding experience and fidelityof their mates. Among first-time breeders, red males achievedthe highest fecundity because of the advantage gained throughearly nesting and pairing with more experienced females andbecause of compensation by their mates for low male provisioningof nestlings. Among experienced breeders, males with intermediateplumage coloration achieved the highest fecundity because ofthe combined benefits of relatively early pairing and high parental care. High variation in sexual ornamentation in a Montana populationof house finches may favor distinct associations of sexualdisplays with a particular set of reproductive behaviors.     

Incubation feeding by male Scarlet Tanagers: a mate removal experiment

ABSTRACT Incubation feeding, where males feed their mates, is a common behavior in birds and may improve female condition, nest attentiveness, and nesting success. We used behavioral observations and a temporary mate removal experiment to test the female nutrition hypothesis for incubation feeding by male Scarlet Tanagers (Piranga olivacea). All males (N= 20) were observed incubation feeding and fed females both at the nest (x? 1.36 trips/h) and away from the nest (x? 20.1 trips/h). Male feeding rate off‐nest was negatively correlated with the duration of female foraging bouts and positively correlated with the total time females spent incubating per hour. Eggs were predated at seven of 19 (37%) nests, but nest survival during incubation was not related to either female incubation behavior or male feeding rate. During temporary removal experiments (N= 12), female Scarlet Tanagers remained on the nest significantly longer and did not have longer foraging bouts. An unexpected outcome of the removal experiments was a dramatic change in female vocal behavior. All 12 experimental females gave chik‐burr calls during the male‐removal experiments (x? bout length = 11.7 min), but during normal observation periods only six of 20 females at the incubation stage gave chik‐burr calls (x? bout length = 0.7 min, N= 20). Our results suggest that female tanagers likely gain nutritional benefits from incubation feeding, but male feeding may not improve immediate reproductive success. Nine of 54 (17%) nestlings in five of 17 broods (29%) were extra‐pair young (EPY), indicating that males could potentially benefit from incubation feeding via mate retention and fidelity as well as, or instead of, through immediate gains in reproductive success. Our study indicates that females benefit from incubation feeding and do not simply passively accept food from their mates, but instead may influence male feeding rates through direct (e.g., mate following and vocalizing) and indirect (the threat of mate abandonment or cuckoldry) means.     

Experimental reduction of incubation temperature affects both nestling and adult blue tits Cyanistes caeruleus

Incubation was for a long time considered to be a period of decreased activity and low cost for parents. It was therefore ignored as a potential factor affecting life‐history trade‐offs in birds. Lately this view has started to change, and studies now show that there might be considerable costs connected to incubation. We experimentally reduced the nest temperature during incubation in blue tits Cyanistes caeruleus, thus increasing the energetic cost of incubation, to test the importance of incubation as a component of reproductive costs and for nestling quality. While most other studies use brood size manipulation to manipulate reproductive costs, we were able to separate treatment effects acting during the incubation period from those acting on later reproductive performance by applying a cross‐foster design. We were also able to isolate the effects of decreased incubation temperature on the nestlings from treatment effects acting on incubating females. We found no experimental effect on the length of the incubation period or on hatching success. The lower temperature during incubation, however, caused lower growth rates in nestlings and reduced chick rearing capacity in adults. We conclude that incubation is a costly period, with the potential to affect both the trade‐off between current and future reproduction and the one between parental effort and offspring quality within the current breeding attempt.     

Effect of alarm calling by male Red‐winged Blackbirds on nestling begging and female provisioning behavior

ABSTRACT Nestling begging and parental provisioning can attract nest predators and reduce reproductive success, so parents and their offspring might be expected to respond adaptively by minimizing predator‐attracting cues when predators threaten nests. Male Red‐winged Blackbirds (Agelaius phoeniceus) are well known for their antipredator alarm calls that contain information about the approach of potential nest predators. We examined the begging behavior of nestlings and the provisioning behavior of females in response to antipredator alarm calls of males to test the adaptive response hypothesis. Playback experiments provided no evidence that alarm calls function to switch off vocal begging; nestlings were equally likely to beg vocally during playback and control periods. Video recordings showed that male alarm calling had no significant effect on inappropriate vocal begging (in the absence of an adult), but significantly reduced the incidence of spontaneous calling (in the absence of begging). Adult females responded to male antipredator alarm calls by delaying their provisioning visits. In addition, although having no significant effect on use of nest‐arriving calls by females, male alarm calling significantly reduced their use of nest‐leaving calls. We conclude that nestling and female Red‐winged Blackbirds respond to male alarm calls in ways that might reduce the risk of predation, but nestlings beg vocally when females arrive to feed them, regardless of male alarm calling, perhaps to avoid a competitive disadvantage with broodmates.     

Azure‐winged Magpies Cyanopica cyanus trade off reproductive success and parental care by establishing a size hierarchy among nestlings

It is common in birds that the sizes of nestlings vary greatly when multiple young are produced in one nest. However, the methods used by parents to establish size hierarchy among nestlings and their effect on parental provisioning pattern may differ between species. In the Azure‐winged Magpie Cyanopica cyanus, we explored how and why parents controlled the sizes of nestlings. Asynchronous hatching was the main cause of size hierarchy within the brood, although the laying of larger eggs later in the laying sequence reduced this effect. Parents with asynchronous broods produced more eggs and fledged more nestlings than those with synchronous broods but their brood provisioning rates, food delivery per feeding bout and feeding efficiency did not differ. We performed a cross‐fostering experiment to synchronize some asynchronous broods. Provisioning rates of asynchronous broods were lower than those of synchronized broods, but the daily growth rates and fledging body mass of their nestlings were not different. Our findings indicate that parents of asynchronous broods can achieve higher reproductive success than those of synchronous broods based on the same parental care, and the same reproductive success as those of synchronized broods based on less parental care. It appears that parent birds can better trade off reproductive success and parental care by establishing a size hierarchy among nestlings.     

Blue structural coloration of male eastern bluebirds Sialia sialis predicts incubation provisioning to females

Plumage coloration has been suggested to serve as an honest signal of benefits that males provide to females. One benefit proposed for females that choose to mate with elaborately colored males is that such males might provide more food resources to the females. To test this hypothesis, we investigated the relationship between the rates at which males provisioned incubating females and the structural ultraviolet (UV)/blue coloration and melanin-based chestnut coloration of male eastern bluebirds Sialia sialis , a sexually dichromatic songbird in which coloration has been shown to be sexually selected in males. We found that males with brighter UV/blue coloration provisioned incubating females more often than did drabber males. Melanin coloration, however, was not correlated with provisioning rates. Moreover, provisioning rates were correlated with the length of time that females spent off the nest, indicating an important benefit of increased male provisioning. These data support the hypothesis that female bluebirds receive direct resource benefits by pairing with males with bright structural coloration.     

Mutual ornamentation and the parental behaviour of male and female Collared Flycatchers Ficedula albicollis during incubation

One of the benefits of mate choice based on sexually selected traits is the greater investment of more ornamented individuals in parental care. The choosy individual can also adjust its parental investment to the sexual signals of its partner. Incubation is an important stage of avian reproduction, but the relationship between behaviour during incubation and mutual ornamentation is unclear. Studying a population of Collared Flycatchers Ficedula albicollis, we monitored the behaviour of both sexes during incubation in relation to their own and their partner's plumage traits, including plumage‐level reflectance attributes and white patch sizes. There was a marginally positive relationship between male feeding rate during incubation and female incubation rate. Female but not male behavioural traits were associated with the laying date of the first egg and clutch size. The behaviour of the two sexes jointly determined the relative hatching speed of clutches and the hatching success of eggs. Females with larger white wing patches spent less time incubating eggs and left the nestbox more frequently. Males with larger white wing patches fed females less frequently, whereas males with brighter white plumage areas visited the nestbox more regularly without feeding. Females tended to leave the nest less often when mated to males with larger wing patches, and females spent less time incubating when males had more UV chromatic plumage. The behaviour of both partners during incubation therefore predicted hatching patterns and was correlated with their own and sometimes with their partner's plumage ornamentation. These results call for further studies of mutual ornamentation and reproductive effort during incubation.     

DIET,HOME RANGE,HUNTING AND REPRODUCTIVE BEHAVIOUR OF A PAIR OF DICKINSON'S KESTREL FALCO DZCKZNSONZ IN THE KRUGER NATIONAL PARK,SOUTH AFRICA

Summary

BENN, G.A. &; KEMP, A.C. 1995. Diet, home range, hunting and reproductive behaviour of a pair of Dickinson's Kestrel Falco dickinsoni in the Kruger National Park, South Africa. Ostrich 66: 81–91.

During July-December 1992, the diet, home range, hunting and reproductive behaviour of a pair of Dickinson's Kestrel Falco dickinsoni was recorded in the Kruger National Park, South Africa. Numerically, for both sexes combined, invertebrates formed the majority (56%) of the diet, while separately the female caught 75% and the male 49% invertebrate prey. During courtship and incubation the male supplied the female with primarily vertebrate prey and both provisioned mainly vertebrates to the nestlings (male = 80%; female = 57%). The non-breeding home range of the female was 27.8 km², and the breeding home range of the male was 26.3 km2. Both utilised their home ranges differentially, the area within a 2 km radius of the nest (12.6 km²) being used proportionally more than the remaining area. The home range of the female was compared to that of other Falco spp. and was larger than would be expected based on body weight. Perch-hunting was the only technique utilised by both sexes, with 79–80% of observed strike attempts from dead trees. During the day, the 9.emale spent 87% and the male 77% of the time perch-hunting, with respective hunting success rates of 69% and 58%. During courtship, the female spent much of her time (94%) close to the nest, where the male supplied her with prey. During incubation, the male spent 95% of his time within 2 km of the nest tree, where he hunted to supply the female with prey at a rate of 0.3 items.hr^?1 and assisted in nest defence. On occasion the male entered the nest to relieve the female, and remained in the cavity on average for 134 min (n = 5). As the young got older, the female spent less time at the nest and provisioned more items to the nestlings. Overall, there was an increase in the rate of prey provisioning to the nestlings from 0.45 items.hr^?1 (10 days old) to 0.85 items.hr^?1 (21 days old). The male initially passed prey to the female but provisioned directly to older nestlings.     

Mate-sharing costs in polygynous Northern Lapwings Vanellus vanellus

In this study bigamous female Northern Lapwings Vanellus vanellus received significantly less incubation relief from their males than monogamous females. On average, monogamous males spent 34.3% of their time incubating and bigamous males 29.9%. Bigamous males divided their effort between their nests, incubating on average 9.4% on primary nests and 20.5% on secondary nests. Bigamous females compensated for the lack of male relief. Primary females incubated for 71.8% of their time, secondary females for 64.2%, while monogamous females spent 52.7% of their time incubating. As a result, there was no significant difference in total nest attentiveness among nests of different status. Primary and secondary females received equivalent incubation relief from the male. Bigamous males increased their contribution to incubation significantly as the season progressed. A bigamous male's distribution of incubation relief between his females was unrelated to female body mass, or to the degree of asynchrony between primary and secondary females in arrival and laying. Incubation time was significantly, negatively, correlated with total nest attentiveness. Monogamous females spent most time, secondary females spent an intermediate time, and primary females spent the least time on maintenance behaviour (foraging, comfort behaviour, inactivity). No significant differences were found in hatching success among females of different mating status. However, the ratio of unhatched to hatched eggs (i.e. the eggs that remained in the nest at the time of hatching) differed significantly: secondary females hatched a smaller proportion of their eggs than monogamous and primary females.     

Incubation feeding as a male tactic for early hatching

Male marsh tits, Parus palustris, regularly feed their mates from the beginning of nest building until hatching. Over three periods (the 15 days preceding egg formation, egg formation/laying and incubation) the number of food passes by the male to the female increased significantly. There was a significant negative relationship between the frequency with which the male fed the female in the nest during incubation and the length of the incubation period. Female blue tits, Parus caeruleus, experimentally supplied with food in the nestbox during incubation had a significantly shorter incubation period than control females. Clutches of experimentally fed females also tended to hatch more successfully. It is concluded that feeding of the female by the male is a nutritional contribution and that the shorter incubation period and increased hatching success enhance the fitness of both parents. However, the male should balance the benefits against the costs in time and energy and therefore not necessarily work at a maximal level. In accordance with this is the finding that the male's provisioning rate increased when ambient temperatures decreased. Adverse weather may jeopardize the whole or large proportions of the clutch, thereby significantly reducing the benefit from the current breeding attempt.     

Mate desertion by male Great Reed Warblers Acrocephalus arundinaceus at the end of the breeding season

Male Great Reed Warblers usually take part in the care of offspring as nest defenders and by feeding young, but at the end of the breeding season they desert their mates with eggs or nestlings. Deserted females continue offspring care. Desertion does not depend on the male's mated status (polygynous or monogamous) nor on his past breeding success. Deserted females compensate for the loss of their partners by increasing the frequency of food-bringing, resulting in a reduction in the amount of time the nestlings are brooded. Although desertion may lead to increased rates of offspring mortality through predation, breeding success of deserted females was high, especially if the male assisted during the early stages. Deserters pay costs by giving up the chance of additional matings and by lowering the reproductive success of existing mates. Male warblers reduce the former cost by choosing the season of desertion and the latter is lowered by the female's high parental ability. A deserter was found to start moulting while his mate was still feeding his nestlings, and an earlier start to the moult may be the primary benefit that he gains. Male Great Reed Warblers usually take part in the care of offspring as nest defenders and by feeding young, but at the end of the breeding season they desert their mates with eggs or nestlings. Deserted females continue offspring care. Desertion does not depend on the male's mated status (polygynous or monogamous) nor on his past breeding success. Deserted females compensate for the loss of their partners by increasing the frequency of food-bringing, resulting in a reduction in the amount of time the nestlings are brooded. Although desertion may lead to increased rates of offspring mortality through predation, breeding success of deserted females was high, especially if the male assisted during the early stages. Deserters pay costs by giving up the chance of additional matings and by lowering the reproductive success of existing mates. Male warblers reduce the former cost by choosing the season of desertion and the latter is lowered by the female's high parental ability. A deserter was found to start moulting while his mate was still feeding his nestlings, and an earlier start to the moult may be the primary benefit that he gains. Male Great Reed Warblers usually take part in the care of offspring as nest defenders and by feeding young, but at the end of the breeding season they desert their mates with eggs or nestlings. Deserted females continue offspring care. Desertion does not depend on the male's mated status (polygynous or monogamous) nor on his past breeding success. Deserted females compensate for the loss of their partners by increasing the frequency of food-bringing, resulting in a reduction in the amount of time the nestlings are brooded. Although desertion may lead to increased rates of offspring mortality through predation, breeding success of deserted females was high, especially if the male assisted during the early stages. Deserters pay costs by giving up the chance of additional matings and by lowering the reproductive success of existing mates. Male warblers reduce the former cost by choosing the season of desertion and the latter is lowered by the female's high parental ability. A deserter was found to start moulting while his mate was still feeding his nestlings, and an earlier start to the moult may be the primary benefit that he gains. Male Great Reed Warblers usually take part in the care of offspring as nest defenders and by feeding young, but at the end of the breeding season they desert their mates with eggs or nestlings. Deserted females continue offspring care. Desertion does not depend on the male's mated status (polygynous or monogamous) nor on his past breeding success. Deserted females compensate for the loss of their partners by increasing the frequency of food-bringing, resulting in a reduction in the amount of time the nestlings are brooded. Although desertion may lead to increased rates of offspring mortality through predation, breeding success of deserted females was high, especially if the male assisted during the early stages. Deserters pay costs by giving up the chance of additional matings and by lowering the reproductive success of existing mates. Male warblers reduce the former cost by choosing the season of desertion and the latter is lowered by the female's high parental ability. A deserter was found to start moulting while his mate was still feeding his nestlings, and an earlier start to the moult may be the primary benefit that he gains. Male Great Reed Warblers usually take part in the care of offspring as nest defenders and by feeding young, but at the end of the breeding season they desert their mates with eggs or nestlings. Deserted females continue offspring care. Desertion does not depend on the male's mated status (polygynous or monogamous) nor on his past breeding success. Deserted females compensate for the loss of their partners by increasing the frequency of food-bringing, resulting in a reduction in the amount of time the nestlings are brooded. Although desertion may lead to increased rates of offspring mortality through predation, breeding success of deserted females was high, especially if the male assisted during the early stages. Deserters pay costs by giving up the chance of additional matings and by lowering the reproductive success of existing mates. Male warblers reduce the former cost by choosing the season of desertion and the latter is lowered by the female's high parental ability. A deserter was found to start moulting while his mate was still feeding his nestlings, and an earlier start to the moult may be the primary benefit that he gains.     

Effects of Shiny Cowbird Molothrus bonariensis parasitism on different components of House Wren Troglodytes aedon reproductive success

Avian brood parasites, including cuckoos and cowbirds, have multiple negative effects on their hosts. We analysed the effects of Shiny Cowbird Molothrus bonariensis parasitism on different components (e.g. egg losses, hatching success, chick survival and nest abandonment) of House Wren Troglodytes aedon reproductive success. We also conducted an experiment to discriminate between two mechanisms that may reduce hatching success in parasitized clutches: lower efficiency of incubation due to the increase in clutch volume and disruption of host incubation by the early hatching of Cowbirds. Egg puncturing by Shiny Cowbirds reduced host clutch size at hatching by 10–20%, and parasitized nests had a decrease in hatching success of 40–80%. Egg losses and hatching failures were positively associated with the intensity of parasitism. Brood reduction was greater in parasitized nests, but the growth rate of the chicks that fledged was similar to that in unparasitized nests. The combined effects of egg losses, hatching failures and brood reduction decreased the number of fledged chicks by 80%. In addition, egg puncturing increased the likelihood of nest abandonment by Wrens. Experimental data showed that hatching failures occurred when there was a combination of: (1) an increase in the volume of the clutch by the addition of the Cowbird egg without removal of host eggs, and (2) the addition of the Cowbird egg before the onset of incubation. This was relatively common in House Wren nests, as Cowbirds generally parasitize before the onset of incubation. Our results indicate that Shiny Cowbird parasitism imposes a major impact on House Wrens, as it affects all components of the Wren's reproductive success.     

Behavioural responses to ectoparasites: time-budget adjustments and what matters to Blue Tits Parus caeruleus infested by fleas

Blue Tit nests are often heavily infested by fleas, which feed on the incubating female and the nestlings. Depending on habitat quality, the drawing of blood by fleas reduces offspring quality, or it is compensated by an increase in food provisioning by the adults and may reduce their future reproduction. Given these fitness costs, tits are expected to have evolved behavioural responses enabling them to remove, destroy or minimize the contact with fleas. To identify these traits, we video-recorded the changes in frequency and duration of the hosts' potential anti-flea behavioural defences in nests experimentally infested with low and high flea densities. We also investigated whether flea load affected the number of male feeds delivered to incubating females, and whether the parents increased their rate of food provisioning to the nestlings equally at high flea density. Flea density significantly affected the nest sanitation and sleeping behaviour of Blue Tit females but had no significant effect on grooming. Female Blue Tits increased the frequency but decreased the duration of bouts of these behavioural traits, and hence their time-budgets, based on per hour duration of behaviour, were not significantly affected by flea density. High flea density reduced nestling weight at the early nestling stage but these costs were fully compensated by an increase in female feeding effort. Males did not increase their frequency of food provisioning to incubating females nor to nestlings in heavily infested nests. The results are discussed in the light of parasite-mediated selection on host behaviour and the reciprocal host selection on flea life-history and behavioural traits.     

Behavioural responses to ectoparasites in pied flycatchers Ficedula hypoleuca: an experimental study

Nests of cavity‐nesting birds usually harbor some species of haematophagous ectoparasites that feed on the incubating adults and nestlings. Given the negative impact of ectoparasites on nestlings there will be selection on hosts to reduce parasite infestations through behavioural means. We have experimentally reduced the abundance of all ectoparasites in nests of pied flycatchers Ficedula hypoleuca to explore both whether there are changes in the frequency and duration of putative anti‐parasite behaviours by tending adults, as well as whether such anti‐parasite behaviours are able to compensate for the deleterious effects that parasites may have on nestlings. Heat treatment of nests substantially decreased the density of ectoparasites, and thereby positively affected nestling growth. The frequency and intensity of female grooming and nest sanitation behaviours during the incubation and nestling periods decreased as a consequence of the experimental reduction of ectoparasite infestation. Although nestlings begged more intensely in infested nests, the experiment had no significant effect on parental provisioning effort. Reduction of parasites resulted in larger nestlings shortly before fledging and increased fledging success. This study shows a clear effect of a complete natural nest ectoparasite fauna on parental behaviour at the nest and nestling growth in a cavity‐nesting bird. Although ectoparasites induce anti‐parasite behaviours in females, these behaviours are not able to fully remove parasite's deleterious effects on nestling growth and survival.     

Effects of down collection on incubation temperature, nesting behaviour and hatching success of common eiders (Somateria mollissima) in west Iceland

Incubating common eiders (Somateria mollissima) insulate their nests with down to maintain desirable heat and humidity for their eggs. Eiderdown has been collected by Icelandic farmers for centuries, and down is replaced by hay during collection. This study determined whether down collecting affected the female eiders or their hatching success. We compared the following variables between down and hay nests: incubation temperature in the nest, incubation constancy, recess frequency, recess duration, egg rotation and hatching success of the clutch. Temperature data loggers recorded nest temperatures from 3 June to 9 July 2006 in nests insulated with down (n = 12) and hay (n = 12). The mean incubation temperatures, 31.5 and 30.7°C, in down and hay nests, or the maximum and minimum temperatures, did not differ between nest types where hatching succeeded. Cooling rates in down, on average 0.34°C/min and hay nests 0.44°C/min, were similar during incubation recesses. Females left their nests 0–4 times every 24 h regardless of nest type, for a mean duration of 45 and 47.5 min in down and hay nests, respectively. The mean frequency of egg rotation, 13.9 and 15.3 times every 24 h, was similar between down and hay nests, respectively. Hatching success adjusted for clutch size was similar, 0.60 and 0.67 in down and hay nests. These findings indicate that nest down is not a critical factor for the incubating eider. Because of high effect sizes for cooling rate and hatching success, we hesitate to conclude that absolutely no effects exist. However, we conclude that delaying down collection until just before eggs hatch will minimize any possible effect of down collection on females.     

Division of labour during incubation in a woodpecker Colaptes auratus with reversed sex roles and facultative polyandry

The contribution of males to incubation has rarely been studied in altricial birds because the pursuit of extra mating opportunities is believed to conflict with incubation. Woodpeckers show reversed sex roles in parental care with males doing most of the nest construction, incubating and brooding of the young while females may be polyandrous. I investigated incubation by each sex at 71 monogamous and four polyandrous nests of the Northern Flicker Colaptes auratus , predicting that males would contribute to incubation according to their energy reserves (body condition) whereas females would contribute based on alternate reproductive opportunities. Nest attendance was 99% with males contributing a mean of 66% of the total incubation including nocturnal incubation. The length of daytime bouts averaged about 2 h and did not differ between the sexes. Consistent with predictions of investment strategies, structurally larger males and those in poorer body condition incubated less than smaller males, perhaps because they required more recess time to forage or to conserve energy. Older females contributed less incubation than young females and polyandrous females contributed less incubation at their secondary nests than monogamous females. Incubation period, nest depredation rate and hatching success were not influenced by bout length, number of bouts or relative contribution of the sexes. Hatching success was 86% at nests of both monogamous and polyandrous females because males compensated for reduced female participation. Because incubation of the sexes is compensatory and not additive, incubation pattern did not influence short-term reproductive success. I conclude that males invest in incubation according to their energy needs, and females may adjust their contributions based on alternate reproductive tactics.