Experimental evaluation of nest shelter effects on weight loss in incubating common eiders Somateria mollissima

Evaluating consequences of habitat selection is an important step in understanding life history strategies and behavioural decisions of animals. Kilpi and Lindström (1997) found that incubating common eiders Somateria mollissima on exposed, treeless islands lost weight faster than females nesting on wooded islands and proposed that this difference was due to adverse incubation conditions at exposed nests. Therefore, we tested whether common eiders gained an advantage when nesting in sheltered habitats by placing artificial shelters over randomly-selected females after the onset of incubation within an eider colony in arctic Canada. We predicted that sheltered females would be heavier on completion of incubation than control hens lacking shelters. Females nesting in artificial shelters experienced a more moderate thermal environment at both cold and warm temperature extremes. Eiders nesting in shelters were heavier than control females during mid incubation, consistent with habitat-specific rates of weight loss reported by Kilpi and Lindström (1997) . Natural overhead cover was available at potential nests but few eiders used those sites. We suspect that microclimatic advantages offered by sheltered sites may be offset by costs of increased female vulnerability to predators. Further work is needed to test this hypothesis, and to determine mechanisms responsible for lower weight loss in eiders attending well concealed nests.     

Favorable spring conditions can buffer the impact of winter carryover effects on a key breeding decision in an Arctic‐breeding seabird

1. The availability and investment of energy among successive life‐history stages is a key feature of carryover effects. In migratory organisms, examining how both winter and spring experiences carryover to affect breeding activity is difficult due to the challenges in tracking individuals through these periods without impacting their behavior, thereby biasing results.
2. Using common eiders Somateria mollissima, we examined whether spring conditions at an Arctic breeding colony (East Bay Island, Nunavut, Canada) can buffer the impacts of winter temperatures on body mass and breeding decisions in birds that winter at different locations (Nuuk and Disko Bay, Greenland, and Newfoundland, Canada; assessed by analyzing stable isotopes of 13‐carbon in winter‐grown claw samples). Specifically, we used path analysis to examine how wintering and spring environmental conditions interact to affect breeding propensity (a key reproductive decision influencing lifetime fitness in female eiders) within the contexts of the timing of colony arrival, pre‐breeding body mass (body condition), and a physiological proxy for foraging effort (baseline corticosterone).
3. We demonstrate that warmer winter temperatures predicted lower body mass at arrival to the nesting colony, whereas warmer spring temperatures predicted earlier arrival dates and higher arrival body mass. Both higher body mass and earlier arrival dates of eider hens increased the probability that birds would initiate laying (i.e., higher breeding propensity). However, variation in baseline corticosterone was not linked to either winter or spring temperatures, and it had no additional downstream effects on breeding propensity.
4. Overall, we demonstrate that favorable pre‐breeding conditions in Arctic‐breeding common eiders can compensate for the impact that unfavorable wintering conditions can have on breeding investment, perhaps due to greater access to foraging areas prior to laying.

     

Re‐colonization by common eiders Somateria mollissima in the Aleutian Archipelago following removal of introduced arctic foxes Vulpes lagopus

Islands provide refuges for populations of many species where they find safety from predators, but the introduction of predators frequently results in elimination or dramatic reductions in island‐dwelling organisms. When predators are removed, re‐colonization for some species occurs naturally, and inter‐island phylogeographic relationships and current movement patterns can illuminate processes of colonization. We studied a case of re‐colonization of common eiders Somateria mollissima following removal of introduced arctic foxes Vulpes lagopus in the Aleutian Archipelago, Alaska. We expected common eiders to resume nesting on islands cleared of foxes and to re‐colonize from nearby islets, islands, and island groups. We thus expected common eiders to show limited genetic structure indicative of extensive mixing among island populations. Satellite telemetry was used to record current movement patterns of female common eiders from six islands across three island groups. We collected genetic data from these and other nesting common eiders at 14 microsatellite loci and the mitochondrial DNA control region to examine population genetic structure, historical fluctuations in population demography, and gene flow. Our results suggest recent interchange among islands. Analysis of microsatellite data supports satellite telemetry data of increased dispersal of common eiders to nearby areas and little between island groups. Although evidence from mtDNA is suggestive of female dispersal among island groups, gene flow is insufficient to account for recolonization and rapid population growth. Instead, near‐by remnant populations of common eiders contributed substantially to population expansion, without which re‐colonization would have likely occurred at a much lower rate. Genetic and morphometric data of common eiders within one island group two and three decades after re‐colonization suggests reduced movement of eiders among islands and little movement between island groups after populations were re‐established. We predict that re‐colonization of an island group where all common eiders are extirpated could take decades.     

Effects of implanted satellite transmitters on behavior and survival of female common eiders

Surgically implanted satellite transmitters have been widely used in studies of avian ecology, yet little is known about their potential impacts on birds. We implanted satellite transmitters with percutaneous antennae (approx. 50 g) in 17 female common eiders (Somateria mollissima) at a breeding colony in Arctic Canada. Among females implanted during incubation, 11 of 12 nests were abandoned within 1 week of being radioed. We observed no differences in the proportion of time that implanted female eiders allocated to basic behaviors. Radioed birds were more likely to pick or preen their abdominal (site of surgical incision) and posterior–dorsal (site of antenna exit) regions than unmarked females, although these behaviors were rare (approx. 0.3% of total time budget). Three of 10 females re-observed had a pronounced limp following surgery, but we observed no walking difficulties among these females in subsequent seasons, and we observed some implanted eiders nesting in subsequent years. Mark–resighting models suggest eiders with transmitters had lower apparent survival the year after implantation (67.0%; 85% CI: 47.8–81.9%) than did color-banded eiders (87.5%, 85% CI: 82.5–91.2%), but there was no model support for a survival difference in subsequent years. We conclude that transmitter implantation in common eiders leads to short-term changes in behavior and a decline in first year survival. We encourage researchers to collect similar data on their study subjects where possible and use it to determine the degree to which data are representative of the greater population. © 2011 The Wildlife Society.     

Reproductive success of solitarily and communally nesting white-footed mice and deer mice

To determine the fitness consequences of communal nesting inwhite-footed mice, Peromyscus leucopus, and deer mice, P. maniculalus,I compared the reproductive success of field populations offemales nesting solitarily, in communal groups of more thanone female, in extended families of successive litters, andin communal groups with extended families. Mean first littersize of weanlings and juveniles 6 weeks old did not differ significantlyfor pups raised under the four nesting situations. Similarly,for pups born into extended families, litter sizes of pups fromsecond litters did not differ significantly from those of firstlitters or from pups born to solitarily nesting females. Delayeddispersal of juvenile females did not result in resource competitionor inhibition of reproduction. Thus, reproductive success offemales was not significantly affected by additional membersin the nest. At least 26 of 28 communally nesting females wereclose relatives. Solitary nesting is the common breeding patternin Peromyscus, and extended families and communal nesting arealternative reproductive tactics in response to limited space,delayed dispersal, and local grouping among related females.     

Colony kin structure and host‐parasite relatedness in the barnacle goose

Conspecific brood parasitism (CBP), females laying eggs in the nest of other ‘host’ females of the same species, is a common alternative reproductive tactic among birds. For hosts there are likely costs of incubating and rearing foreign offspring, but costs may be low in species with precocial chicks such as waterfowl, among which CBP is common. Waterfowl show strong female natal philopatry, and spatial relatedness among females may influence the evolution of CBP. Here we investigate fine‐scale kin structure in a Baltic colony of barnacle geese, Branta leucopsis, estimating female spatial relatedness using protein fingerprints of egg albumen, and testing the performance of this estimator in known mother‐daughter pairs. Relatedness was significantly higher between neighbour females (nesting ≤ 40 metres from each other) than between females nesting farther apart, but there was no further distance trend in relatedness. This pattern may be explained by earlier observations of females nesting close to their mother or brood sisters, even when far from the birth nest. Hosts and parasites were on average not more closely related than neighbour females. In 25 of 35 sampled parasitized nests, parasitic eggs were laid after the host female finished laying, too late to develop and hatch. Timely parasites, laying eggs in the host’s laying sequence, had similar relatedness to hosts as that between neighbours. Females laying late parasitic eggs tended to be less related to the host, but not significantly so. Our results suggest that CBP in barnacle geese might represent different tactical life‐history responses.     

Do common eiders nest in kin groups? Microgeographic genetic structure in a philopatric sea duck

We investigated local genetic associations among female Pacific common eiders (Somateria mollissima v‐nigrum) nesting in a stochastic Arctic environment within two groups of barrier islands (Simpson Lagoon and Mikkelsen Bay) in the Beaufort Sea, Alaska. Nonrandom genetic associations were observed among nesting females using regional spatial autocorrelation analyses for distance classes up to 1000 m in Simpson Lagoon. Nearest‐neighbour analyses identified clusters of genetically related females with positive lr values observed for 0–13% and 0–7% of the comparisons in Simpson Lagoon and Mikkelsen Bay, respectively, across years. These results indicate that a proportion of females are nesting in close proximity to more genetically related individuals, albeit at low frequency. Such kin groupings may form through active association between relatives or through natal philopatry and breeding site fidelity. Eiders nest in close association with driftwood, which is redistributed annually by seasonal storms. Yet, genetic associations were still observed. Microgeographic structure may thus be more attributable to kin association than natal philopatry and site fidelity. However, habitat availability may also influence the level of structure observed. Regional structure was present only within Simpson Lagoon and this island group includes at least three islands with sufficient driftwood for colonies, whereas only one island at Mikkelsen Bay has these features. A long‐term demographic study is needed to understand more fully the mechanisms that lead to fine‐scale genetic structure observed in common eiders breeding in the Beaufort Sea.     

Aggressive neighbors and dense nesting: nest site choice and success in high-Arctic common eiders

Minimizing the risk of nest predation has led some bird species to exploit the nest defense behavior of other species. At Nasaruvaalik Island, Nunavut, Canada, some common eiders (Somateria mollissima borealis) nest within the boundaries of Arctic tern (Sterna paradisaea) colonies, while others nest elsewhere on the island, away from the terns. We tested the effects of location (within vs. outside the tern colonies), density of common eider nests, and annual variation on the nesting parameters of common eiders. Our results suggest that nesting in association with Arctic terns does not confer an obvious benefit to eiders. Such associative nesting of eiders and terns may be the result of overlapping habitat preferences between the two species, or a general scarcity of suitable nesting habitat for ground-nesting species in the high Arctic. However, eiders nesting in higher densities with other eiders had greater nest success and lower total clutch predation, indicating a positive correlation between nest density and success.     

Early arrival, initiation of nesting, and social status: an experimental study of breeding female red-winged blackbirds

Red-winged blackbirds (Agelaius phoeniceus) arrive at breedingsites several months before nests are constructed. Males inthis highly polygynous species presumably return early to defenddesirable territories. Females, however, also begin to arrivealmost two months before nesting is attempted. Early returnto breeding sites could enhance reproductive success by increasinga female's social status and thereby allowing earlier nesting.I measured the effect of experimentally delayed arrival on thetiming of nesting, reproductive success, and social status offemales. Birds were captured as they arrived in early springand detained in an aviary. These experimental females were laterreleased at their capture sites before control females beganconstruction of nests; controls had arrived during the sameperiod as experimentals but were not detained. Experimentalfemales nested, on average, more than a week later than controls,although I could detect no effect of timing on reproductivesuccess during this study. By manipulating arrival date, butnot covariates of arrival time such as age or experience, thisresult indicates that timing of arrival directly influencedlaying date. Delayed females were subordinate to control femaleswith the same mate. This decline in social status may have beenresponsible for the delay in nesting and could have fitnessconsequences for females in some years, because the offspringof earlier nesting, dominant birds are more likely to receivemale parental care in this population.     

Colony Development and Serial Polygyny in the Primitively Eusocial Wasp Belonogaster juncea juncea (Vespidae: Polistinae)

In Cameroon, the social ropalidiine wasp Belonogaster juncea juncea mostly selects human constructions for nesting, but nests installed in the shelter of large boulders were also noted. Nests were founded throughout the year by one female (25.5%) or by associations of two to eight females. Among the 49 colonies studied from foundation, 24 produced at least one adult, and only 5 produced males among the eight that succeeded in producing sexual individuals. After the first dominant female disappeared (died or abandoned the nest, from 77 to 196 days after foundation) the remaining females fought among themselves, leading to a drastic decrease in the total number of brood. They completely abandoned 22 of 24 surviving nests, over a mean colony cycle lasting about 7 months. Hence the colony and nesting cycles were congruent, illustrating that determinate nesting corresponds to the majority of the cases in this species. In the other two nests, some females remained on the nest and began a new colonial cycle illustrating semi-independence between colony and nesting cycles. Up to four successive cycles were completed in this way in the same nest, thus illustrating the phenomenon of serial polygyny (intermediate between determinate and indeterminate nesting cycles). Serial polygyny in independent founding polistine wasps, previously documented only once, has implications for studies attempting to identify factors involved in regulating the colony and nesting cycles in tropical social wasps.     

Plasma mammalian leptin analogue predicts reproductive phenology,but not reproductive output in a capital‐income breeding seaduck

To invest in energetically demanding life history stages, individuals require a substantial amount of resources. Physiological traits, particularly those related to energetics, can be useful for examining variation in life history decisions and trade‐offs because they result from individual responses to environmental variation. Leptin is a protein hormone found in mammals that is proportional to the amount of endogenous fat stores within an individual. Recently, researchers have confirmed that a mammalian leptin analogue (MLA), based on the mammalian sequence of leptin, is present with associated receptors and proteins in avian species, with an inhibitory effect on foraging and body mass gain at high circulating levels. While MLA has been both quantified and manipulated in avian species, little is currently known regarding whether plasma MLA in wild‐living species and individuals is associated with key reproductive decisions. We quantified plasma MLA in wild, Arctic‐nesting female common eiders (Somateria mollissima) at arrival on the breeding grounds and followed them to determine subsequent breeding propensity, and reproductive phenology, investment, and success. Common eiders are capital‐income breeding birds that require the accumulation of substantial fat stores to initiate laying and successfully complete incubation. We found that females with lower plasma MLA initiated breeding earlier and in a shorter period of time. However, we found no links between plasma MLA levels and breeding propensity, clutch size, or reproductive success. Although little is still known about plasma MLA, based on these results and its role in influencing foraging behaviors and condition gain, plasma MLA appears to be closely linked to reproductive timing and is therefore likely to underlie trade‐offs surrounding life history decisions.     

Brood parasitism,female condition and clutch reduction in the common eider Somateria mollisima

Conspecific brood parasitism (CBP) is an alternative reproductive tactic found in many animals with parental care. Parasitizing females lay eggs in the nests of other females (hosts) of the same species, which incubate and raise both their own and the foreign offspring. The causes and consequences of CBP are debated. Using albumen fingerprinting of eggs for accurately detecting parasitism, we here analyse its relation to female condition and clutch size in High Arctic common eiders Somateria mollissima borealis. Among 166 clutches in a Svalbard colony, 31 (19%) contained eggs from more than one female, and 40 of 670 eggs (6%) were parasitic. In 6 cases an active nest with egg(s) was taken over by another female. Many suitable nest sites were unoccupied, indicating that CBP and nest takeover are reproductive tactics, not only consequences of nest site shortage. Similarity in body mass between female categories suggests that condition does not determine whether a nesting female becomes parasitised. There was no evidence of low condition in parasites: egg size was similar in hosts and parasites, and parasitism was equally frequent early and late in the laying season. Meta‐analysis of this and 3 other eider studies shows that there is a cost of being parasitised in this precocial species: host females laid on average 7% fewer eggs than other females.     

Strong constraints to independent nesting in a facultatively social bee: quantifying the effects of enemies-at-the-nest

Constraints to independent nesting play a key role in the understanding of social evolution in insects, but the source and the magnitude of such constraints are poorly known for many key taxa. In allodapine bees it is known that solitary nesting females have low rates of successful brood rearing and that this drives selection for cooperative nesting. It has been hypothesized that these constraints are due to the presence of enemies-at-the-nest, such as ants, but no direct link has been demonstrated between such enemies and colony failure. We set up an experiment in which solitary founded nests of an Australian allodapine bee, Exoneura nigrescens, were either protected from non-flying predators or left unprotected, and compared the resulting colony survival and brood production rates. We found that protected colonies have much higher rates of survival and that the constraints to independent nesting are extreme, with a mean of less than one offspring per nest at the end of the brood rearing period. This means that cooperative nesting is essential for this species to persist in its habitat. Received 6 July 2007; revised 5 November 2007; accepted 12 November 2007.     

Male mating strategies and the mating system of great-tailed grackles

Great-tailed grackles (Quiscalus mexicanus) are sexually dimorphic,dichromatic, colonially nesting blackbirds. In this study, males pursued three basic types of conditional mating strategies,each of which employed a different set of mating tactics. Territorialmales defended one or more trees in which several females nested.They achieved reproductive success by siring the offspringof their social mates and through extrapair fertilization.Resident males lived in the colony but did not defend territoriesor have social mates. Transient males passed through the colony, staying no more than a few days, and probably visited more thanone colony. Residents appeared to queue for access to territories,but transients did not. Residents and transients gained allpaternity through extrapair fertilizations and provided noparental care. Territorial males sired the majority of offspring,but residents and transients also sired small numbers of nestlings. Territorial males were larger and had longer tails than nonterritorialmales. The number of social mates was related to body size,and males that sired nestlings were heavier and had longertails than males with no genetic reproductive success. Malesthat gained paternity through extrapair fertilization wereheavier and had longer tails than males that did not. The matingsystem of great-tailed grackles can best be categorized as "non-faithful-female frank polygyny."     

Host-parasite relationships in six species ofSphecodes bees and their halictid hosts: Nest intrusion,intranidal behavior,and Dufour's gland volatiles (Hymenoptera: Halictidae)

Nest invasion behavior was studied in six kleptoparasiticSphecodes species at four nesting sites of their respective social and solitary hosts.Sphecodes females preferred to enter unguarded nests. Nest intruding strategies observed in the differentSphecodes species did not depend on whether host species were solitary or social, as long as the nesting cycle of a social host was in the solitary stage (i.e., a single host female). Observation of intranidal behavior revealed thatSphecodes monilicornis females kill all host individuals within an usurped nest. They stay in the nest for several hours, laying eggs in adequately provisioned brood cells. Gas chromatography-mass spectrometry analyses of Dufour's gland secretions revealed species-specific compositions. Qualitative comparisons of whole patterns and quantitative comparisons considering the predominant hydrocarbons common to both host and parasite contradict the hypothesis of chemical mimetism, a mechanism supposed to permit parasite intrusion by qualitatively similar odor bouquets in host and parasite females.     

Spatial-genetic structuring in a red-breasted merganser (Mergus serrator) colony in the Canadian Maritimes

The clustering of kin is widespread across the animal kingdom and two of the primary mechanisms underlying the formation of these patterns in adult kin are (1) philopatric tendencies and (2) actively maintained kin associations. Using polymorphic microsatellites, we had set out to characterize the level of genetic-spatial organization within a colony of female red-breasted mergansers (Mergus serrator) breeding on a series of small barrier islands in Kouchibouguac National Park, NB, Canada. Additionally, using nesting data from this colony, we explored possibilities for the existence of kin associations and/or cooperative interactions between these individuals; specifically in the form of the synchronization of breeding activities (i.e., incubation initiation). Our results include: (1) the detection of broad-scale genetic structuring over the entire colony, as females nesting on separate islands were to some extent genetically distinct; (2) the detection of weak, yet significant, positive spatial autocorrelation of kin at the fine scale, but only in the more densely-populated areas of this colony; and (3) the synchrony of breeding activities among proximally nesting females, apart from any factors of relatedness. While these results confirm the existence of genetic-spatial organization within this colony, the underlying mechanisms producing such a signal are inconclusive.     

Social interactions among wild female Bechstein's bats (<Emphasis Type="Italic">Myotis bechsteinii</Emphasis>) living in a maternity colony

Although sociality is common in bats, few studies have investigated individual social behaviour in free-ranging colonies. This study quantifies social interactions among wild female Bechstein's bats (Myotis bechsteinii) belonging to one maternity colony. Our main goal was to analyse allogrooming and nose rubbing, which are both regularly displayed by adult females. Based on data of individually marked bats with known degrees of pairwise relatedness, we suggest that allogrooming has both a social and a hygienic function. Females groomed colony mates mainly on parts of the body that are difficult to reach by a bat itself. Thus, allogrooming may function to remove ectoparasites from inaccessible body parts. Allogrooming was rare compared to self-grooming (on average 0.7% vs 37.7% of a female's total observation time), and there was no significant correlation between the rate at which a bat groomed itself and the frequency with which it was groomed by conspecifics. Therefore, we assume that allogrooming also has a social purpose in addition to its assumed hygienic function. We suggest that allogrooming could strengthen social bonds among colony members that live together for many years. Mothers and adult daughters groomed each other preferentially. Thus, allogrooming may reflect special mother–daughter bonds. Nose rubbing occurred mainly within minutes (median: 80 s) after the arrival of a female in a night roost, and there was no correlation with relatedness. Therefore, it probably allows recognition of colony mates and may also be a greeting behaviour. Communicated by M.E. dos Santos     

Male and Female Parental Roles in the Monogamous Cichlid, Tilapia mariae, Introduced in Florida

We documented male and female parental roles of a monogamous fish, the spotted tilapia, Tilapia mariae, in channelized rivers in southern Florida, where this species dominated the fish fauna within 10 years of their introduction. Clearly differentiated parental roles existed between males and females, with females performing nearly all tending of embryos and most tending of free embryos. After young became free-swimming and left the nest, however, males took over primary tending of the school of young while the female patrolled the perimeter of the school and performed nearly all chases directed at predators. Male and female T. mariae also traded off vigilance and feeding, and showed a high degree of intrapair coordination. Experimental removal of one or both parents had major effects on parental behavior and brood survival and integrity. Solitary females took on a parental role intermediate between that of the male and female of a pair. Untended broods were attacked by predators and scattered into aquatic vegetation, and were not observed to reform. Under dense nesting conditions we observed adoption of broods, group rearing of free-swimming young and the presence of non-breeder satellites sharing and defending a territory with breeders. This highly complex parental care may have allowed T. mariae to invade fish communities dominated by uniparental centrarchids, as well as allowing them to use disturbed habitats such as channelized rivers that are of poor quality for nesting and rearing offspring.     

Male rank, female breeding synchrony, and patterns of paternity in the boat-tailed grackle

Species in which males directly defend groups of breeding femalesoften have extreme skew in observed male mating success. Inonly a few species, however, has a corresponding skew in fertilizationsuccess been confirmed. Furthermore, the ecological and socialfactors contributing to variation in fertilization success needinvestigation. This study examined competition for mates andpaternity in the boat-tailed grackle (Quiscalus major). Observationsat colonies of nesting females revealed that the toprankingor alpha males performed more than 70% of the copulations. DNAfingerprinting indicated that alpha males sired less than 40%of nestlings. Nevertheless, analysis of band-sharing scoresamong nestlings from different nests suggested that alpha malessired more than three times as many offspring as any other individualmale. Because few nestlings were sired by the nonalpha malesthat associated with colonies, females must have mated withother males while on trips away from colonies. Analysis of paternitywithin broods revealed that at least half of all females hadtheir brood fertilized by more than one male. Alpha males' successat fertilizing eggs did not vary with the number of simultaneouslyreceptive females within a colony. Our results suggest that maleand female behavior in female-defense polygyny results fromcomplex coevolution of the sexes.