Population dynamics and habitat preference of two urbanized Columbidae species and their nest predator in two settlement types

Since urbanization is a worldwide phenomenon, numerous species have gained the advantage of urban ecosystems. The Eurasian Collared Doves (Streptopelia decaocto) has become widespread all across Europe along with human-altered habitats. In general, population levels are stable but numbers have locally decreased in the past few decades. In parallel, a new wave of urbanization came forward, so Wood Pigeons (Columba palumbus) entered urban ecosystems alongside with other Columbidae species. In this paper, our primary goal was to find any connection between habitat availability factors such as coniferous tree density and the population dynamics of two urbanized species. A locally emerging corvid species, the Hooded Crow (Corvus cornix) was also taken into consideration in influencing tree-nesting doves and pigeons as a primary nest predator. During the research period, we aimed to express the differences in habitat structure of two urban ecotypes by nesting tree availability and structure and to prove the power of predator presence in sampling sites. Our results showed that residential areas have a higher proportion of coniferous trees, as well as the high preference of residential areas by Wood Pigeons and Eurasian Collared Doves.

Development of polygynous colonies of Messor muticus ants in laboratory conditions

The process of growing a family of reaper ants Messor muticus (Nylander, 1849) in a test tube incubator according to the method proposed by G.M. Dlussky and M.P. Bukin (1986) considers its structure and principle of operation. The queens were captured during the flight and identified in accordance with the phylogenetic analysis of F. Steiner. The test ant colonies were divided into 3 experimental and one control groups. The main factors influencing the polygyny development of ant colonies, such as nest size and temperature are considered. The features of the destructive behavior of worker ants and their participation in the regulation of oviparous queens number in the family, as well as the influence of pheromone activity on the relationship between workers and reproductive individuals are described. The main goal of the experiment was to confirm the theory of the effect of nest size and temperature on the development of dimatological colonies of a species with a monogyny family structure. The experiment was carried out for 71 days, observations were recorded every week, the results were summed up on the 8th and 10th weeks of the experiment. The conclusion confirms the theoretical assumptions about the influence of temperature and the size of the primary nest on the development of polygynous colonies of reaper ants Messor muticus. The data obtained can serve as a basis for further study of polygyny in ant colonies, ants behavior in an unnatural habitat and the existence of ants under controlled conditions.

Socio-ecological factors shape the opportunity for polygyny in a migratory songbird

Why females pair with already mated males and the mechanisms behind variation in such polygynous events within and across populations and years remain open questions. Here, we used a 19-year data set from a pied flycatcher (Ficedula hypoleuca) population to investigate, through local networks of breeding pairs, the socio-ecological factors related to the probability of being involved in a polygynous event in both sexes. Then, we examined how the breeding contexts experienced by individuals shaped the spatial and temporal separation between broods of polygamous males. The probability of polygyny decreased with the distance between nests. Indeed, secondary females were often close neighbors of primary females, although the distance between both nests increased slightly with increasing synchrony between them. The probability of polygyny was also related to the breeding time of individuals because early breeding males were more likely to become polygynous with late-breeding females. Throughout the season, there was substantial variation in the temporal separation between primary and secondary broods, and this separation was, in turn, related to the breeding asynchrony of the polygamous males (in the primary nest) relative to the neighbors. Polygynous males that bred late relative to their neighbors had a short time window to attract a second female and, thus, the breeding interval between their primary and secondary broods was reduced. Overall, the spatial proximity between polygynous males’ broods and, if the opportunity existed, their temporal staggering are compatible with a male strategy to maximize paternity and reduce the costs of caring for two broods, though the effect of female’s interest, either primary or secondary, cannot be fully ruled out. We highlight that a comprehensive assessment of the breeding contexts faced by individuals is essential to understand mating decisions and reconcile the discrepancies raised by previous work on social polygyny.

Crying wolf to a predator: deceptive vocal mimicry by a bird protecting young

Animals often mimic dangerous or toxic species to deter predators; however, mimicry of such species may not always be possible and mimicry of benign species seems unlikely to confer anti-predator benefits. We reveal a system in which a bird mimics the alarm calls of harmless species to fool a predator 40 times its size and protect its offspring against attack. Our experiments revealed that brown thornbills ( Acanthiza pusilla ) mimic a chorus of other species' aerial alarm calls, a cue of an Accipiter hawk in flight, when predators attack their nest. The absence of any flying predators in this context implies that these alarms convey deceptive information about the type of danger present. Experiments on the primary nest predators of thornbills, pied currawongs ( Strepera graculina ), revealed that the predators treat these alarms as if they themselves are threatened by flying hawks, either by scanning the sky for danger or fleeing, confirming a deceptive function. In turn, these distractions delay attack and provide thornbill nestlings with an opportunity to escape. This sophisticated defence strategy exploits the complex web of interactions among multiple species across several trophic levels, and in particular exploits a predator's ability to eavesdrop on and respond appropriately to heterospecific alarm calls. Our findings demonstrate that prey can fool predators by deceptively mimicking alarm calls of harmless species, suggesting that defensive mimicry could be more widespread because of indirect effects on predators within a web of eavesdropping.

Clutch size and initiation date of ospreys: natural patterns and the effect of a natural delay

We studied the breeding performance of ospreys (Pandion haliaetus) in southeastern British Columbia from 1987 to 1990. Clutch size, brood size, and the number of young fledged per nest all declined significantly as clutch initiation date was delayed. The quality of later born young as measured by growth rate and the number of fault bars in rectrices did not seem to be reduced. Behavioural observations of the flight-hunting performance of six focal males demonstrated that food availability did not decline in the course of the nestling period. Clutch initiation of some osprey pairs was naturally delayed when their nests were occupied by Canada geese (Branta canadensis). Nest occupation delayed clutch initiation by 9.4 days on average, and reduced clutch size by 0.2 eggs. Osprey pairs possessing an alternate nest were not delayed by the presence of geese in their primary nest, and did not reduce clutch size, suggesting that the clutch size reduction was a direct response to the delay, rather than to the presence, of geese. The results do not support the reduced food availability or reduced breeding commitment hypotheses for seasonal clutch size decline. The data conform to the predictions of the hypothesis that the optimal clutch size is set by a trade-off between the declining reproductive value of later hatched nestlings and the delay required to be able to enlarge the clutch.