Colonial Nesting Research Articles

Social Cues and Environmental Conditions Influence Foraging Flight Distances of Breeding Wood Storks (Mycteria americana)

Abstract. The influence of both environmental conditions and social cues on the distance flown to foraging sites was examined for breeding Wood Storks (Mycteria americana) in the Florida Everglades, USA. Adult Wood Storks (n= 73) were followed in a small plane from their nesting colony to their foraging locations during the time when adult Wood Storks were incubating and feeding chicks. On average, foraging sites were close to the nesting colony (mean = 9.6 km ± 1.1), and in shallow water (mean = 9.9 cm ± 0.7) that was receding at a moderate rate (-0.36 cm/day ± 0.13). Wood Storks landed at foraging sites already occupied by other white wading birds 99% of the time, with a mean flock size of 64 ± 14 birds. Model selection identified flock size and water recession rate as the most important variables that influenced Wood Stork foraging flight distances. Distances flown to foraging sites increased with increasing flock sizes and decreased with increasing recession rates (increasing by 39% and decreasing by ...

Kendermagos réce (Anas strepera) telepes fészkelése a Nyugat-Dunántúlon

Kendermagos réce (Anas strepera) telepes fészkelése a Nyugat-Dunántúlon

Geographic segregation and evidence of density-dependent changes in sex ratios in an abundant colonial waterbird.

Demographic information, such as geographic segregation of sexes and sex ratio data, is needed to develop, model and evaluate conservation and management strategies for wildlife. A variety of physiological, behavioral and environmental factors can influence segregation of sexes and sex ratios, many of which originate with density-dependent processes. Departure from 50:50 sex ratios of double-crested cormorants (Phalacrocorax auritus) collected during control efforts in breeding and wintering areas across their eastern range of the USA were evaluated using using a Z-test as well as Stouffer's weighted Z-tests. In addition, a specifically-designed randomization test was used to evaluate density-dependent effects on primary sex ratios in cormorants from egg collections and colony nest count data over a 21-year period. Cormorants collected from breeding colonies were strongly male-biased, whereas cormorants collected from feeding flocks were slightly biased toward females. Cormorants were partly segregated by sex on the wintering grounds, with significantly more males found in areas with intensive channel catfish aquaculture. The null hypothesis that females produced a balanced sex ratio independent of number of nesting cormorants was rejected: more male embryos were produced during rapid population growth, whereas at maximum nesting number more female embryos were produced. Once populations stabilized, the sex ratio was more equal. This examination of sex ratios indicates that different management methods and locations result in sex-biased culling of cormorants. Sex-biased culling in cormorants could make population reduction efforts more efficient and reduce overall take. We suggest further research to examine density-dependent effects on primary sex ratios documented here.

Mapping sleeping bees within their nest: spatial and temporal analysis of worker honey bee sleep.

Patterns of behavior within societies have long been visualized and interpreted using maps. Mapping the occurrence of sleep across individuals within a society could offer clues as to functional aspects of sleep. In spite of this, a detailed spatial analysis of sleep has never been conducted on an invertebrate society. We introduce the concept of mapping sleep across an insect society, and provide an empirical example, mapping sleep patterns within colonies of European honey bees (Apis mellifera L.). Honey bees face variables such as temperature and position of resources within their colony's nest that may impact their sleep. We mapped sleep behavior and temperature of worker bees and produced maps of their nest's comb contents as the colony grew and contents changed. By following marked bees, we discovered that individuals slept in many locations, but bees of different worker castes slept in different areas of the nest relative to position of the brood and surrounding temperature. Older worker bees generally slept outside cells, closer to the perimeter of the nest, in colder regions, and away from uncapped brood. Younger worker bees generally slept inside cells and closer to the center of the nest, and spent more time asleep than awake when surrounded by uncapped brood. The average surface temperature of sleeping foragers was lower than the surface temperature of their surroundings, offering a possible indicator of sleep for this caste. We propose mechanisms that could generate caste-dependent sleep patterns and discuss functional significance of these patterns.

At home with the birds:Kalahari tree skinks associate with sociable weaver nests despiteAfrican pygmy falcon presence

AbstractThe way in which animals use habitat can affect their access to key resources or how they are buffered from environmental variables such as the extreme temperatures of deserts. One strategy of animals is to modify the environment or take advantage of structures constructed by other species. The sociable weaver bird (Philetairus socius) constructs enormous colonial nests in trees. These nests are frequented by Kalahari tree skinks (Trachylepis spilogaster) and the two species coexist over a large portion of theKalahariDesert inSouthAfrica. We tested whether skinks were more abundant in trees containing sociable weaver nests and asked whether the physical features of trees were important predictors of skink abundance. We then focused on potential costs of this association by examining the relationship between skink abundance and the presence of a potential predator, the pygmy falcon (Polihierax semitorquatus), which exclusively uses weaver nest colonies for roosting and nesting. Finally, we simulated a predatory threat to determine if skinks assess risk differently if a weaver nest is present. We found a significant positive association between the presence of weaver nests and skink abundance. In the absence of nests, the type of tree did not influence skink abundance. Skinks used weaver nests and were more likely to perch on the nest than the tree. When threatened with predation, skinks preferred to take refuge in nests. Surprisingly, the presence of nesting pygmy falcons in nests did not influence skink abundance, perhaps because of the abundance of nearby refuges within nests, tree crevices, or in debris at the tree base. We suggest that sociable weaver nests provide multiple benefits to skinks including lowered predation risk, thermal refuges and greater prey availability, although this requires experimental testing. In the current era of global climate change, sociable weaver nests may become a crucial resource for skinks seeking refuge as theKalahari climate warms.

The fossil record of bird behaviour

AbstractBetween the Middle Jurassic and Holocene, birds evolved an enormous diversity of behaviours. The distribution and antiquity of these behaviours is difficult to establish given a relatively poor fossil record. Rare crop, stomach and gut contents typically reveal diets consistent with morphology but stem‐members of some lineages (including Cariamae and Coraciiformes) seem to have been different in ecology from their extant relatives. Most of our ideas about the behaviour of fossil birds are based on analogy (with skull form, limb proportions and claw curvature being used to guide hypotheses). However, this has limitations given that some extinct taxa lack extant analogues and that some extant taxa do not behave as predicted by osteology. Reductionist methods have been used to test predation style and running ability in fossil taxa including moa, Gastornis and phorusrhacids. Virtually nothing is known of nesting and nest‐building behaviour but colonial nesting is known from the Cretaceous onwards. Rare vegetative nests demonstrate modern nest‐building from the Eocene onwards. Ornamental rectrices indicate that sexually driven display drove some aspects of feather evolution and evidence for loud vocal behaviour and intraspecific combat is known for some taxa. Our knowledge of fossil bird behaviour indicates that ‘modern’ behaviours are at least as old as crown birds. Stem‐members of extant lineages, however, may sometimes or often have differed from extant taxa.

A context-dependent alarm signal in the ant Temnothorax rugatulus.

Because collective cognition emerges from local signaling among group members, deciphering communication systems is crucial to understanding the underlying mechanisms. Alarm signals are widespread in the social insects and can elicit a variety of behavioral responses to danger, but the functional plasticity of these signals has not been well studied. Here we report an alarm pheromone in the ant Temnothorax rugatulus that elicits two different behaviors depending on context. When an ant was tethered inside an unfamiliar nest site and unable to move freely, she released a pheromone from her mandibular gland that signaled other ants to reject this nest as a potential new home, presumably to avoid potential danger. When the same pheromone was presented near the ants' home nest, they were instead attracted to it, presumably to respond to a threat to the colony. We used coupled gas chromatography/mass spectrometry to identify candidate compounds from the mandibular gland and tested each one in a nest choice bioassay. We found that 2,5-dimethylpyrazine was sufficient to induce rejection of a marked new nest and also to attract ants when released at the home nest. This is the first detailed investigation of chemical communication in the leptothoracine ants. We discuss the possibility that this pheromone's deterrent function can improve an emigrating colony's nest site selection performance.

Resource redistribution in polydomous ant nest networks: local or global?

An important problem facing organisms in a heterogeneous environment is how to redistribute resources to where they are required. This is particularly complex in social insect societies as resources have to be moved both from the environment into the nest and between individuals within the nest. Polydomous ant colonies are split between multiple spatially separated, but socially connected, nests. Whether, and how, resources are redistributed between nests in polydomous colonies is unknown. We analyzed the nest networks of the facultatively polydomous wood ant Formica lugubris. Our results indicate that resource redistribution in polydomous F. lugubris colonies is organized at the local level between neighboring nests and not at the colony level. We found that internest trails connecting nests that differed more in their amount of foraging were stronger than trails between nests with more equal foraging activity. This indicates that resources are being exchanged directly from nests with a foraging excess to nests that require resources. In contrast, we found no significant relationships between nest properties, such as size and amount of foraging, and network measures such as centrality and connectedness. This indicates an absence of a colony-level resource exchange. This is a clear example of a complex behavior emerging as a result of local interactions between parts of a system.

Hurricane, Habitat Degradation, and Land Loss Effects on Brown Pelican Nesting Colonies

Walter, S.T.; Carloss, M.R.; Hess, T.J., and Leberg, P.L., 2013. Hurricane, habitat degradation, and land loss effects on Brown Pelican nesting colonies.Nesting colonies of coastal avifauna are perennially threatened by hurricanes, land loss, and environmental contamination. To understand how nest substrate and habitat availability influence reproductive success of Brown Pelicans (Pelecanus occidentalis), we monitored 802 nests and quantified vegetation cover on two barrier islands in Louisiana from 2008 to 2010. In 2008, Hurricanes Gustav and Ike caused habitat degradation and land loss at our study sites and thus allowed comparison of pelican productivity in pre- and post-hurricane conditions. As habitat availability changed across years and islands, pelicans shifted from nesting in woody vegetation, to grasses, forbs, and bare ground. More chicks that survived until the age of 3 to 4.5 weeks old were from higher nests, and the loss of woody vegetation might have elicited colony abandonment. Habitat reduction was attributed to hurricane-induced erosion, and shoreline retreat was an average 5.5 times (range 3.3 to 11) greater than regional rates from 1887 to 2002. Furthermore, land loss (16% to 99% of vegetated regions) was restricted to areas without protective breakwaters. In addition to the effects of habitat decline on pelican reproduction, contamination by the Deepwater Horizon oil spill might have further decreased nest success. Large and productive seabird colonies can be rapidly degraded by both human and natural disturbance, making amelioration of such threats a management priority.

Potential adverse effects of inorganic pollutants on clinical parameters of loggerhead sea turtles (Caretta caretta): Results from a nesting colony from Cape Verde, West Africa

A large number of nesting loggerhead sea turtles (n = 201) were sampled to establish the blood levels of 11 elements (Cu, Mn, Pb, Zn, Cd, Ni, Cr, As, Al, Hg, and Se). Almost all of the samples showed detectable levels of these 11 elements, and Zn and Se exhibited the highest concentrations (median values as high as 6.05 and 2.28 μg/g, respectively). The median concentrations of the most toxic compounds, As, Cd, Pb, and Hg, were relatively low (0.38, 0.24, 0.06, and 0.03 μg/g, respectively). We also determined the haematological and biochemical parameters in a subsample of 50 turtles to evaluate the potential effects of these contaminants on clinical parameters and found several associations. Our study reinforces the usefulness of blood for the monitoring of the levels of contaminating elements and their adverse effects on blood parameters in sea turtles.

Harvester ants use interactions to regulate forager activation and availability

Social groups balance flexibility and robustness in their collective response to environmental changes using feedback between behavioural processes that operate at different timescales. Here we examine how behavioural processes operating at two timescales regulate the foraging activity of colonies of the harvester ant, Pogonomyrmex barbatus, allowing them to balance their response to food availability and predation. Previous work showed that the rate at which foragers return to the nest with food influences the rate at which foragers leave the nest. To investigate how interactions inside the nest link the rates of returning and outgoing foragers, we observed outgoing foragers inside the nest in field colonies using a novel observation method. We found that the interaction rate experienced by outgoing foragers inside the nest corresponded to forager return rate, and that the interactions of outgoing foragers were spatially clustered. Activation of a forager occurred on the timescale of seconds: a forager left the nest 3-8 s after a substantial increase in interactions with returning foragers. The availability of outgoing foragers to become activated was adjusted on the timescale of minutes: when forager return was interrupted for more than 4-5 min, available foragers waiting near the nest entrance went deeper into the nest. Thus, forager activation and forager availability both increased with the rate at which foragers returned to the nest. This process was checked by negative feedback between forager activation and forager availability. Regulation of foraging activation on the timescale of seconds provides flexibility in response to fluctuations in food abundance, whereas regulation of forager availability on the timescale of minutes provides robustness in response to sustained disturbance such as predation.

Factors associated with bluegill nest site selection within a shallow, natural lake

Information regarding nest site selection for bluegill (Lepomis macrochirus) is limited. Therefore, our study identified important characteristics of bluegill nest sites in a shallow, natural lake - West Long Lake, Nebraska, USA, on the Valentine National Wildlife Refuge. Bluegill nest colonies were identified visually from a boat and nine abiotic and seven vegetative variables were measured at both nest colony sites and randomly selected sites (i.e., no active bluegill colonies at random sites). Measurements of six variables differed between nest and random sites, suggesting that these variables may be influential in the nest selection process for bluegill. These variables included submersed macrophyte species, submersed macrophyte coverage, distance to nearest submersed macrophytes, water temperature, distance to shore and maximum southern fetch. In contrast to other studies, nest site substrate composition was not different between nesting sites and random sites. Our results indicate that nesting substrate may not be limiting to bluegill in West Long Lake. Rather, other characteristics (e.g., submersed macrophytes and protection from wind) appear to play a larger role in determining bluegill nest site selection in our study lake.

A Large Accumulation of Avian Eggs from the Late Cretaceous of Patagonia (Argentina) Reveals a Novel Nesting Strategy in Mesozoic Birds

We report the first evidence for a nesting colony of Mesozoic birds on Gondwana: a fossil accumulation in Late Cretaceous rocks mapped and collected from within the campus of the National University of Comahue, Neuquén City, Patagonia (Argentina). Here, Cretaceous ornithothoracine birds, almost certainly Enanthiornithes, nested in an arid, shallow basinal environment among sand dunes close to an ephemeral water-course. We mapped and collected 65 complete, near-complete, and broken eggs across an area of more than 55 m2. These eggs were laid either singly, or occasionally in pairs, onto a sandy substrate. All eggs were found apparently in, or close to, their original nest site; they all occur within the same bedding plane and may represent the product of a single nesting season or a short series of nesting attempts. Although there is no evidence for nesting structures, all but one of the Comahue eggs were half-buried upright in the sand with their pointed end downwards, a position that would have exposed the pole containing the air cell and precluded egg turning. This egg position is not seen in living birds, with the exception of the basal galliform megapodes who place their eggs within mounds of vegetation or burrows. This accumulation reveals a novel nesting behaviour in Mesozoic Aves that was perhaps shared with the non-avian and phylogenetically more basal troodontid theropods.

Do Ants Need to Estimate the Geometrical Properties of Trail Bifurcations to Find an Efficient Route? A Swarm Robotics Test Bed

Interactions between individuals and the structure of their environment play a crucial role in shaping self-organized collective behaviors. Recent studies have shown that ants crossing asymmetrical bifurcations in a network of galleries tend to follow the branch that deviates the least from their incoming direction. At the collective level, the combination of this tendency and the pheromone-based recruitment results in a greater likelihood of selecting the shortest path between the colony's nest and a food source in a network containing asymmetrical bifurcations. It was not clear however what the origin of this behavioral bias is. Here we propose that it results from a simple interaction between the behavior of the ants and the geometry of the network, and that it does not require the ability to measure the angle of the bifurcation. We tested this hypothesis using groups of ant-like robots whose perceptual and cognitive abilities can be fully specified. We programmed them only to lay down and follow light trails, avoid obstacles and move according to a correlated random walk, but not to use more sophisticated orientation methods. We recorded the behavior of the robots in networks of galleries presenting either only symmetrical bifurcations or a combination of symmetrical and asymmetrical bifurcations. Individual robots displayed the same pattern of branch choice as individual ants when crossing a bifurcation, suggesting that ants do not actually measure the geometry of the bifurcations when travelling along a pheromone trail. Finally at the collective level, the group of robots was more likely to select one of the possible shorter paths between two designated areas when moving in an asymmetrical network, as observed in ants. This study reveals the importance of the shape of trail networks for foraging in ants and emphasizes the underestimated role of the geometrical properties of transportation networks in general.

Immune Responses of a Native and an Invasive Bird to Buggy Creek Virus (Togaviridae: Alphavirus) and Its Arthropod Vector, the Swallow Bug (Oeciacus vicarius)

Invasive species often display different patterns of parasite burden and virulence compared to their native counterparts. These differences may be the result of variability in host-parasite co-evolutionary relationships, the occurrence of novel host-parasite encounters, or possibly innate differences in physiological responses to infection between invasive and native hosts. Here we examine the adaptive, humoral immune responses of a resistant, native bird and a susceptible, invasive bird to an arbovirus (Buggy Creek virus; Togaviridae: Alphavirus) and its ectoparasitic arthropod vector (the swallow bug; Oeciacus vicarius). Swallow bugs parasitize the native, colonially nesting cliff swallow (Petrochelidon pyrrhonota) and the introduced house sparrow (Passer domesticus) that occupies nests in cliff swallow colonies. We measured levels of BCRV-specific and swallow bug-specific IgY levels before nesting (prior to swallow bug exposure) and after nesting (after swallow bug exposure) in house sparrows and cliff swallows in western Nebraska. Levels of BCRV-specific IgY increased significantly following nesting in the house sparrow but not in the cliff swallow. Additionally, house sparrows displayed consistently higher levels of swallow bug-specific antibodies both before and after nesting compared to cliff swallows. The higher levels of BCRV and swallow bug specific antibodies detected in house sparrows may be reflective of significant differences in both antiviral and anti-ectoparasite immune responses that exist between these two avian species. To our knowledge, this is the first study to compare the macro- and microparasite-specific immune responses of an invasive and a native avian host exposed to the same parasites.

Determining the amount of water condensed above and below the winter cluster of honey bees in a North—European Climate

SummaryThe amount of water condensed in the hives of overwintering honey bee colonies was investigated. In autumn, condensers of thin sheet metal were placed in hives above and below the frames of the winter nests of the experimental colonies. The condensed water could flow into plastic bottles for collection. Most of the water collected during the winter condensed on the lower devices, only 2.5 ± 1.31% on the upper ones. At an average food consumption of 7.17 ± 0.35 kg, the amount of water condensed was 445.27 ± 45.8 g. The total amount of water released by such food consumption would be 4.88 ± 0.24 kg. The upper condensers increased moisture and wet surfaces in the hive, whereas the lower ones did not. Test and control colonies did not differ significantly in food consumption and bee mortality. The top condenser created additional airspace above the cluster and probably metabolic water vapour released from the cluster, having risen up first started descending, but due to the longer distance to the lower condenser it cooled more and condensed on the hive walls. The results show that in hives without top ventilation, it would be appropriate to remove descended water vapour from below of the nest or to retain it in the hive for spring consumption of the bees. It enables to reduce humidity in the nest of bees without strengthened ventilation to withdraw increased heat loss and enforces the bees to rise the metabolic rate and heat production, which in turn would increase food consumption and water production.

Predator–prey interactions between the South Polar skua Catharacta maccormicki and Antarctic tern Sterna vittata

Antarctic terns have to co‐exist in a limited space with their major nest predator, the skuas. We conducted artificial nest experiments to evaluate the roles of parental activity, nest location and nest and egg crypsis in this simple predator–prey system. Predation on artificial (inactive) nests was higher in traditional nesting sites than in sites previously not occupied by terns, which suggests that skuas memorized past tern breeding sites. Predation on artificial nests in inactive colonies was higher than in active (defended) colonies. Parental defense reduced predation in colonies to the level observed in artificial nests placed away from colonies. This suggests that communal defense can balance the costs of attracting predators to active colonies. Within colonies, predation was marginally higher on experimental eggs put in real nests than on bare ground. Although it seems that the presence of a nest is costly in terms of increased predation, reductions in nest size might be constrained by the need for protective nest structures and/or balanced by opposing selection on nest size. Predation did not differ markedly between artificial (quail) and real tern eggs. A simultaneous prey choice experiment showed that the observed predation rates reflected egg/nest detectability, rather than discrimination of egg types. In summary, nesting terns probably cannot avoid being detected, and they cannot defend their nest by attending them. Yet, by temporarily leaving the nest, they can defend it through communal predator mobbing, and at the same time, they can benefit from crypsis of unattended nest and eggs.

The Role of the Harvester Termite,Trinervitermes trinervoides(Termitidae: Nasutitermitinae), in a Semi-Arid Grassland Ecosystem in South Africa: Nest Populations and Caste Composition

Nest populations or colonies of the harvester termite, Trinervitermes trinervoides (Sjostedt) (Termitidae: Nasutitermitinae), which commonly occurs in the semi-arid grasslands of southern Africa, were assessed. The entire contents of nests, mounds and subterranean sections were excavated following fumigation. Termites were extracted by flotation from volumetric sub-samples of the nest material and counted. Nest populations were found to be considerably larger than those of other members of the genus. Sterile adult populations varied from 9000 in small mounds (height = 12 cm) to 889 000 in large mounds (height = 59 cm). Workers, major and minor soldiers make up 75%, 9% and 16%, respectively, of the total adult sterile population. The proportion of soldiers decreased with increasing colony size, constituting 51% of populations of the smallest nest and only 16% of a large nest. This decrease in total soldier proportions in larger nests reflected a decrease in the proportion of minor soldiers. Ratios of worke...

Colonial nesting of red-footed falcon Falco vespertinus L. in near lake Manych-Gudilo

The peculiarities of the colonial nesting of the red-footed falcon Falco vespertinus L. in the valley of Manych-Gudilo Lake, such as the dynamics of the relative population, productivity, and population characteristics (clutch size, oological variability, breeding success, etc.) depending on the colonial structure, weather and climate fluctuations, the boundary effect, and anthropogenic factors have been studied.

Mercury Exposure May Suppress Baseline Corticosterone Levels in Juvenile Birds

Mercury exposure has been associated with a wide variety of negative reproductive responses in birds, however few studies have examined the potential for chick impairment via the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis regulates corticosterone levels during periods of stress. We examined the relationship between baseline fecal corticosterone metabolite concentrations and mercury concentrations in down feathers of recently hatched (<3 days) and blood of older (15-37 days) Forster's tern (Sterna forsteri) chicks in San Francisco Bay, California. Baseline fecal corticosterone metabolite concentrations were negatively correlated with mercury concentrations in blood of older chicks (decreasing by 81% across the range of observed mercury concentrations) while accounting for positive correlations between corticosterone concentrations and number of fledgling chicks within the colony and chick age. In recently hatched chicks, baseline fecal corticosterone metabolite concentrations were weakly negatively correlated with mercury concentrations in down feathers (decreasing by 45% across the range of observed mercury concentrations) while accounting for stronger positive correlations between corticosterone concentrations and colony nest abundance and date. These results indicate that chronic mercury exposure may suppress baseline corticosterone concentrations in tern chicks and suggests that a juvenile bird's ability to respond to stress may be reduced via the downregulation of the HPA axis.