Pairs Of Birds Research Articles

Non-photoperiodic factors and timing of breeding in blue tits: Impact of environmental and social influences in semi-natural conditions

The seasonal development of life-history traits is influenced by many environmental factors. The impact of photoperiodic and non-photoperiodic factors on nest building and egg laying has been rarely investigated in non-domesticated avian species for which long term field data sets are available. Former investigations showed that blue tits originating from geographically close populations in the Mediterranean region do not respond in the same way to photoperiodic factors in semi-natural outdoor conditions. Here we show experimentally that nest building and onset of egg laying in captive blue tits is also proximately influenced by non-photoperiodic factors, including aspects related to aviary characteristics and social interactions between birds of the two sexes originating from different local Mediterranean study populations. In two successive experiments, we show that (1) increasing the volume of the aviary advanced the egg laying period of one specific population by almost 1 month, and (2) crossing pairs of birds from different origins strongly reduced the nest building and egg laying behaviours. These results indicate that obtaining biologically relevant breeding results in captivity with wild birds requires the control and experimental manipulation of a wide array of complex environmental cues.

Fighting kites: behaviour as a key to species identity in wall scenes

The species of an ambiguous pair of birds represented in the Saqqara tomb of nj-‘nhḫ-ẖnmw and ẖnmw-ḥtp has been determined by examination of the animals’ distinctive postures.

Influence of body size on coexistence of bird species

AbstractTheory suggests that body size is an important factor in determining interspecific competition and, ultimately, in structuring ecological communities. However, there is a lack of pragmatic studies linking body size and interspecific competition to patterns in ecological communities. The objective of the present study was to determine the effect of body size (mass) on competitive interactions between bird pairs and to investigate the influence of food guilds. Point‐counts were carried out in nine sites every month from November 2002 to November 2003 in the Cuetzalan Region, Mexico, and we used presence/absence and abundance data for the analyses. To calculate the strength of competition we used the Angle Frequency Method to extract form factors from 20 pairwise interactions. A prototype competition interaction and random pairs were also constructed. We used clustering techniques (PCA) to calculate the dissimilarity scores (distances,D) of each of the pairwise interactions to the prototype competition and random pairs and one‐way ANOVA to test for differences between the means of the random and competitive pairs. The ratio in body mass (lnBM) for each of the interacting pairs was calculated, and the association between the lnBM ratio and the strength of competition (D) was tested using a Pearson product‐moment correlation coefficient. To test for the influence of foraging guilds we used a univariate general linear model. Our results demonstrate a significant negative relationship between bird body mass ratio and competition strength – i.e. competition strength increased when the body masses of the birds became more similar. We did not find a significant influence of foraging guild on the relationship between body mass ratio and competition strength. On the basis of these results, we suggest that high variation in body sizes amongst sympatric species promotes coexistence in communities.

Have Winter Spacing Patterns of Harlequin Ducks Been Partially Shaped by Sexual Selection?

Abstract Sexual selection can operate throughout the annual cycle and likely shapes the winter plumage and courtship displays of many northern waterfowl that choose mates during winter. Less conspicuous effects of sexual selection are likely and in this study I asked whether winter distribution patterns and grouping behavior of Harlequin Ducks (Histrionicus histrionicus) are partially shaped by sexual selection. Harlequin Ducks are typically dispersed in small groups and observed grouping behavior supported the hypothesis that unpaired adult and immature birds will show sexually-selected changes in their spacing to facilitate courtship and mate sampling. Unpaired birds occurred in larger groups than paired birds during October-February, and group-related differences in the sex ratio and in the proportion of females that were unpaired indicated that unpaired birds were aggregating specifically for courtship. Behavior similar to lekking was observed at one site. Males gathered at this site at daybreak, unpa...

Blood metabolite levels in normal and handicapped pied flycatchers rearing broods of different sizes

We measured levels of select metabolites (glucose, triglycerides, free fatty acids, glycerol, uric acid) and corticosterone in the blood plasma of adult pied flycatchers Ficedula hypoleuca while they were rearing broods whose sizes were modified experimentally. We also made it more difficult than normal for some pairs of birds to forage by removing certain wing and tail feathers (handicapping them). Both procedures have been shown previously to change parental workload. We did this in order to determine if the birds alter their use of nutrients in response to differences in their workload. Metabolite levels were not influenced by handicapping or brood size. However, the concentration of free fatty acids in the plasma of females and of triglycerides in the plasma of males was directly related to the frequency with which the adults fed their nestlings. These findings suggest that the two sexes have different ways of coping with the work associated with rearing the brood: females apparently undergo brief daily fasts while feeding their chicks, whereas males take more time to feed themselves while providing food for their young, and spend more time doing so as their workload increases. The flycatchers exhibited high concentrations of uric acid and corticosterone in the blood plasma; corticosterone and glycerol were positively correlated in females; and corticosterone and triglyceride levels were negatively correlated in males; all of which suggest that gluconeogenesis provides some of the energy required for their parental activities.

COMPARATIVE SPRING MIGRATION ARRIVAL DATES IN THE TWO MORPHS OF WHITE-THROATED SPARROW

White-throated Sparrows (Zonotrichia albicollis) display a plumage dimorphism (white-striped and tan-striped) with attendant behavioral differences, including greater aggression levels in white-striped birds and negative assortative mating, in which tan-striped birds pair with white-striped birds. To determine whether morph influences migration timing, which could influence patterns of assortative mating, we evaluated the phenology of northbound migration among White-throated Sparrows from a long-term banding dataset collected at a southern Ontario banding station. White-throated Sparrows are sexed by wing-chord length, but there is an intermediate size for which sex cannot be assigned. When all birds were considered together (both known and unknown sexes, n = 6,243), the white-striped birds migrated earlier by slightly more than 2 days. The sexing criteria, however, appeared to yield a sample that was not representative of the whole population: when we included only birds for which sex was assigned (n = 2,794, 45% of all birds), white-striped birds apparently migrated earlier by more than 4 days, but separate analyses of males (n = 1,511) and females (n = 1,283) revealed no differences in migration timing between morphs. By measuring wing-chord lengths of internally sexed specimens (from the Royal Ontario Museum) collected during April to June (n = 273), we found that in both sexes the wings of white-striped birds were about 2% longer than those of tan-striped birds. When we used these specimen data to recalibrate the sexing criteria, (a) it was possible to assign sex to 1.47 times as many birds (n = 4,121; 66% of all birds), (b) sex ratios of the banded birds more closely approached what appears to be the natural sex ratio (approximately 1:1), and (c) within-sex analyses indicated that white-striped females migrate earlier than tan-striped females by about 1.3 days, whereas there was no statistical difference between male morphs in migration timing.

Florida Scrub‐Jays Compensate for the Sentinel Behavior of Flockmates

AbstractSentinel coordination requires that individuals react to the sentinel behavior of others. Previous work showed that Florida scrub‐jays are sentinels more often when given supplemental food. Here we measured how birds in pairs reacted when their mates were fed. Scrub‐jays were sentinels less when their mates were fed, demonstrating compensation. Indirect evidence suggests that this compensatory decrease in sentinel behavior was smaller than the increase in sentinel behavior by their mates. In addition, males in newly established groups were sentinels less often.

The Duet Code of the Female Black-Bellied Wren

Abstract In many duet-singing songbirds, paired birds combine their song types nonrandomly to form duet songs. Several different behavioral mechanisms could generate nonrandom song type associations in duets. I tested female Black-bellied Wrens (Thryothorus fasciatoventris) for one such mechanism: adherence to a set of rules linking female response songs to male stimulus songs. I call this set of rules a “duet code.” Duets of free-living Black-bellied Wrens were recorded in 2001 and 2002. In 2003 I returned to the same territories and played the male song types from the recorded duets. Females answered male song stimuli as if duetting with the playback speaker. Although the known repertoires of females averaged 8.4 song types, each female sang only a single song type in response to each male song type. Random answering could not account for this pattern, supporting the hypothesis that females abide by duet codes. Females that were still paired with their mates from 2001–2002 answered 100% of their mate's songs with the same song types they had used previously, demonstrating that codes are stable over time. In contrast, females that were new to a territory answered an average of only 18% of their mate's song types with the same song type as the previous female, indicating that duet codes are individually distinctive. Duet participation by female Black-bellied Wrens represents a special kind of animal communication, in which discrete vocal signals consistently elicit discrete vocal responses according to an individually distinctive set of rules.

Predator-elicited visual signal: why the turquoise-browed motmot wag-displays its racketed tail

Both sexes of the turquoise-browed motmot (Eumomota superciliosa) perform a wag-display in the presence of predators, whereby their long racketed tail is repeatedly rocked side-to-side in a pendulous fashion. I tested 3 hypotheses for the function of the predator-elicited wag-display: 1) pursuit-deterrent signal, 2) warning alarm signal, and 3) self-preservation alarm signal. These hypotheses were evaluated by testing whether the presence of potential receivers (kin, conspecifics, mate) modified the way in which the wag-display was performed. Data on wag-display were collected when I experimentally presented predators to motmots and when naturally occurring predators were observed at nesting colonies. The wag-display was performed by male and female motmots who were 1) alone and not within signaling distance of conspecifics, 2) unpaired and therefore not signaling to a mate, and 3) paired but away from their mate. Motmots in these contexts performed the wag-display with similar probability and in a similar manner as individuals that were within signaling distance of conspecifics, paired birds, and paired birds who were near their mate. These results support the hypothesis that the predator-elicited wag-display is directed to the predator and functions as a pursuit-deterrent signal. Key words: alarm signaling, antipredator behavior, predator-elicited signaling, predator‐prey communication, pursuit-deterrent signaling, tail plumage. [Behav Ecol]

Dominance rank influences food hoarding in New Zealand Robins Petroica australis

Social interactions are thought to be an important determinant of food hoarding behaviour in birds. Theoretical work predicts that subordinate birds should cache more to offset losses to dominant birds. However, empirical support for this prediction is mixed. We evaluated whether social dominance influences the food hoarding behaviour of New Zealand Robins Petroica australis. Robins provide a unique opportunity to test food hoarding theory because they are fearless of humans and will cache food presented to them by hand. We offered mealworms to free‐ranging male and female Robins to test whether (1) one sex was socially dominant, (2) the subordinate sex cached more frequently than the dominant sex and (3) birds cached more frequently when they were in the presence of a potential competitor. Our results indicate that males were dominant over females. Males acquired most of the prey offered to birds during trials and won all aggressive encounters observed between sexes. However, caching rates ran contrary to theoretical predictions. Males stored approximately twice as many mealworms as females. Both sexes also stored more food when they were alone than when they were accompanied by conspecifics. We interpret the reluctance of females and paired birds to hoard food as a strategy to avoid the loss of caches to competitors. Our overall results indicate that dominance rank strongly influences caching decisions, but that caching rates ran contrary to theoretical predictions.

Senescence effects in an extremely long-lived bird: the grey-headed albatrossThalassarche chrysostoma

Studies attempting to document reproductive or other pre-lethal senescence effects in wild birds typically face an array of problems, including flaws in statistical analyses, non-adaptive philopatry to deteriorating environments, confounding effects arising from cohort heterogeneity and differential death rates of phenotypes and the frequent pairing of old birds to younger mates. Furthermore, recent studies suggest that birds could maintain a high level of physical fitness until old age, before being struck by a catastrophic illness leading quickly to their demise. The presence of terminally ill individuals in most datasets (and their greater incidence in older age categories) may therefore provide a false impression of progressive senescence in cross-sectional analyses. This study was designed explicitly to avoid all the known pitfalls linked to the demonstration of progressive senescence in wild populations, and involved one of the very longest-lived bird species. We show that, during incubation, old (aged 35 years and over) male grey-headed albatrosses Thalassarche chrysostoma make longer foraging trips, and have lower daily mass gains, than experienced mid-aged individuals (aged up to 28 years). This is, to our knowledge, the first report documenting reduced foraging performance with old age. Hatching and breeding success of pairs composed of two old individuals were reduced in comparison to mid-aged pairs. Overall results were very similar when analyses were repeated using only individuals known to have survived 1 or 2 years beyond field measurements (hence probably not suffering from the effects of an advanced terminal illness). We conclude that extremely long-lived individuals usually experience some degree of general physical deterioration, leading to reduced foraging and breeding performance, long before their final demise.

Home-range size of Pyrenean grey partridges Perdix perdix hispaniensis during the breeding season

We investigated spacing patterns of Pyrenean grey partridges Perdix perdix hispaniensis during the breeding season (March-September) to refine our recommendations concerning restoration of nesting and brood rearing habitats. The study was based on 30 grey partridges, 24 yearlings (19 males, five females) and six adults (five males, one female) radio-monitored in two study areas of the eastern Pyrenees. Movements and home ranges were analysed for the pre- and post-hatching periods. For each bird and period, we used cluster analysis to identify core areas within home ranges. Throughout the breeding season, 24 of the 30 birds were paired and six yearling males remained unpaired. The latter used larger home ranges than paired birds, at least before hatching. The home-range size (Minimum Convex Polygon) of the 24 pairs averaged 118 ha in spring (from pair formation to hatching) and 126 ha in summer (brood-rearing period). Pairs tended to use larger core areas after hatching (mean = 10.8 ha) than before (mean = 6.2 ha). After hatching, broodless pairs used larger core areas (mean = 14.4 ha) than those with broods (mean = 8.7 ha). For both groups, we found little overlap between core areas used before and after hatching. For unsuccessful breeders, the small overlap was associated with post-breeding movements to higher altitudes. For successful breeders, it was related to movements to brood rearing habitat. Daily inter-fix distances of broods averaged 126 m during the first three weeks after hatching, then regularly increased up to 249 m as chicks exceeded the age of six weeks. The size of core areas used by broods indicates that treatment plots should cover 5–10 ha to restore breeding habitats with a diversity of shrubland vegetation types.

EFFECTS OF HUMAN RECREATION ON THE INCUBATION BEHAVIOR OF AMERICAN OYSTERCATCHERS

Human recreational disturbance and its effects on wildlife demographics and behavior is an increasingly important area of research. We monitored the nesting success of American Oystercatchers (Haematopus palliatus) in coastal North Carolina in 2002 and 2003. We also used video monitoring at nests to measure the response of incubating birds to human recreation. We counted the number of trips per hour made by adult birds to and from the nest, and we calculated the percent time that adults spent incubating. We asked whether human recreational activities (truck, all-terrain vehicle ;obATV;cb, and pedestrian traffic) were correlated with parental behavioral patterns. Eleven a priori models of nest survival and behavioral covariates were evaluated using Akaike's Information Criterion (AIC) to see whether incubation behavior influenced nest survival. Factors associated with birds leaving their nests (n = 548) included ATV traffic (25%), truck traffic (17%), pedestrian traffic (4%), aggression with neighboring oystercatchers or paired birds exchanging incubation duties (26%), airplane traffic (1%) and unknown factors (29%). ATV traffic was positively associated with the rate of trips to and away from the nest (β1 = 0.749, P < 0.001) and negatively correlated with percent time spent incubating (β1 = −0.037, P = 0.025). Other forms of human recreation apparently had little effect on incubation behaviors. Nest survival models incorporating the frequency of trips by adults to and from the nest, and the percentage of time adults spent incubating, were somewhat supported in the AIC analyses. A low frequency of trips to and from the nest and, counter to expectations, low percent time spent incubating were associated with higher daily nest survival rates. These data suggest that changes in incubation behavior might be one mechanism by which human recreation affects the reproductive success of American Oystercatchers.

Advertising by western grebes: bout-length variability and signal confusion in a multiple-use call

Studies of song variability in birds have contributed greatly to our understanding of how animals use vocal signals to communicate information concerning their individual identity, species, sex, and territorial or pairing status to other members of the population. Most of these studies have focused on the songs of male passerine songbirds, where learning plays an important role in the development of song variability. Here we examine variability within a multi-functional call of a nonpasserine species, the western grebe (Aechmophorus occidentalis). In this observational study, we focused on variability in the lengths of consecutive call-bouts given by individuals within different behavioral contexts. Early in the breeding season, Advertising appeared to serve as an initial contact between two lone courting birds, which then approached and eventually engaged one another in visual displays. After pairing, however, both sexes continued to use Advertising calls in a variety of contexts that involved mate recognition or parent-young communication. Cases of signal confusion or misidentification of pairing status were rare and generally brief, even within the contexts of a large colony. During the pre-nesting period, unpaired birds usually gave bouts of 3-5 calls, while paired birds gave 1- or 2-call bouts. During incubation, birds returning to their nests often Advertised repeatedly to their mate using 1- or 2-call bouts in nearly equal proportions. Replies by their mate from the nest were more likely to be 2- or 3-call bouts (74%) and appeared to guide the returning bird to the nest. Finally, post-nesting parents calling to their young or mates primarily used 1- or 2-call bouts. We suggest that bout-length flexibility likely plays an important role in providing redundancy in a noisy environment and in limiting signal confusion in this multi-functional call.

THE DUET CODE OF THE FEMALE BLACK-BELLIED WREN

Abstract In many duet-singing songbirds, paired birds combine their song types nonrandomly to form duet songs. Several different behavioral mechanisms could generate nonrandom song type associations in duets. I tested female Black-bellied Wrens (Thryothorus fasciatoventris) for one such mechanism: adherence to a set of rules linking female response songs to male stimulus songs. I call this set of rules a “duet code.” Duets of free-living Black-bellied Wrens were recorded in 2001 and 2002. In 2003 I returned to the same territories and played the male song types from the recorded duets. Females answered male song stimuli as if duetting with the playback speaker. Although the known repertoires of females averaged 8.4 song types, each female sang only a single song type in response to each male song type. Random answering could not account for this pattern, supporting the hypothesis that females abide by duet codes. Females that were still paired with their mates from 2001–2002 answered 100% of their mate's ...

Identifying contact zone hotspots of passerine birds in the Palaearctic region

Birds are known to be a group rich in pairs of closely related species that have parapatric or allopatric distributions with relatively narrow contact zones. Here we analyse the geographical distribution of these contact zones for parapatric species pairs of passerine birds of the Palaearctic region. Their contact zones are located mainly in southwestern, northern and central-southern Asia, and in northwestern Africa, with a hotspot in the Middle East. A mid-domain effect null model, where contact zone hotspots are a neutral correlate of continental geometry, had a low explanatory power of 3.8%; the observed distribution of contact zones was not sufficiently predicted. Hypotheses involving range contractions and secondary contact in areas of high topographic and habitat diversity may offer more convincing explanations and offer promising perspectives for future studies.

Quantitative review of the diet of the Purple-bellied parrotTriclaria malachitaceaat Loro Parque Fundación, Tenerife

In Brazil the wild population of Purple-bellied parrot Triclaria malachitacea is in decline. The species is seldom found in zoological collections because it is difficult to maintain in captivity. At the beginning of 1998 Loro Parque Fundacion, Tenerife, maintained 21 (9.10.2) birds, c. 35% of the T. malachitacea population maintained in captivity outside the country of origin. Analyses of the basic diet offered, the food that was not consumed and the excrement of five pairs of birds over 5 days were carried out to determine the nutritional content of the diet offered and consumed. The ingested diet was found to have an excessive concentration of metabolizable energy and crude protein, and the calcium/phosphorous ratio was found to be lower than the minimum recommended in the literature. The digestibility values for dry matter, crude protein, crude fat, crude fibre, NfE (nitrogen free extract) and starch were calculated for T. malachitacea.

First pairing in Snow GeeseAnser caerulescens: at what age and at what time of year does it occur?

In migratory birds, the place and time of pair formation are important parameters for population structure and dynamics. Geese are not only migratory but also exhibit long‐term monogamy, and therefore the first pairing event in a bird's lifetime is of particular importance. Through behavioural observations of young, known‐age, marked birds conducted on the wintering grounds during three winter seasons we investigated two aspects of the timing of first pair formation in the Wrangel Island population of Snow GeeseAnser caerulescens: (1) the age at which birds first form pair bonds, and (2) the seasonal pattern of first pair formation. Wrangel Island Snow Geese paired considerably later in life than Snow Geese from a low‐Arctic population: almost none of the birds formed pairs in their second winter, and many were still in sibling groups for at least part of that season. The proportion of birds in pairs continued to increase until at least 5 years of age. Most pairing took place during the observation periods, and in general the proportion of birds in pair bonds increased gradually throughout the winter season. The amount of pairing during spring migration or summer varied annually and among cohorts, indicating that even very young birds may be able to form pair bonds quickly if conditions on the breeding grounds are unusually favourable. Pairing later and remaining in family groups longer may be a response to breeding conditions in this high‐Arctic colony. Here, productivity is typically low due to harsh weather and predation, whereas Snow Geese breeding in the low Arctic are less restricted and form pairs and start to breed when younger. The fact that most, but not all, pairing takes place on the wintering grounds helps explain why a previous study found a certain amount of gene flow between the two Wrangel Island subpopulations with separate wintering grounds.

Multiple‐brooding in birds of prey: South African Black Sparrowhawks Accipiter melanoleucus extend the boundaries

Multiple‐brooding (raising more than one brood of young in quick succession) occurs infrequently in raptors and is generally restricted to either smaller species with shorter nesting periods, co‐operative breeders or species capable of capitalizing on conditions of prolonged food abundance whenever they occur. This paper presents the first recorded cases of multiple‐brooding in the Black Sparrowhawk Accipiter melanoleucus from two distinct locales in South Africa. In the Western Cape (Cape Peninsula), four attempts to multiple‐brood were recorded in four different years, involving three distinct pairs of birds, and in KwaZulu–Natal (Eshowe), three distinct pairs of Sparrowhawks successfully multiple‐brooded on several occasions over a 5‐year study period. These results establish the Black Sparrowhawk as one of only two relatively large, monogamous raptor species, and the only specialist bird‐eating raptor, in which multiple‐brooding has been recorded with any frequency. The species’ capacity to thrive in human‐modified environments (i.e. alien plantations) and particularly to exploit associated foraging opportunities (e.g. high densities of doves and pigeons in suburban areas) may, at least partly, account for the instances of multiple‐brooding reported here. We suggest that biologists be more vigilant for cases of multiple‐brooding in raptors, as it is possible that this trait is more common than originally thought and has previously been overlooked.

Timing of Breeding in the Feral PigeonColumba liviaf.domesticain Słupsk (Nw Poland)

The study was conducted from 1997–2001 in the city of Słupsk. Observations of individually marked birds were conducted from blinds located at city-centre sites where Feral Pigeons breed. The pigeons bred throughout the year, with peak broods in spring and summer. Different pairs timed their breeding such that the beginning of the season (from October to September of the next calendar year) overlapped the dates of completion (from April to December). 10% of pairs had already begun breeding in the autumn, while 86% did so between January and May. The remaining pairs (young ones, in particular) started breeding even later, mainly because of the lack of suitable nesting sites. The breeding period most often ended between August and October (75% of pairs), when the pigeons began their moult. 91% of the young birds joined the breeding population in their second calendar year of life. The remaining young birds had their first broods in the first or third calendar year of life. Pairs of young birds started nesting 2–3 months later than adult birds. The average length of a pair's breeding season was 183 days.