Avian nests are crucial to reproduction as they are the site for incubation of the clutch of eggs and, in many cases, it is the location for the rearing of chicks hatched. Despite many years of reports of the characteristics of nests from many species our understanding of their functional properties has been very poor. Over the past few years, interest in the functional properties of nests has increased and this review brings together information regarding how materials used to construct the nest contribute to various functional properties. The review starts with a brief consideration of the various functions of nests but thereafter the focus is on the key roles that it plays during incubation. Details of the variety of materials used in nest construction emphasises the importance of quantitative data on the types and amounts of materials used in nests and how this information allows analysis that can improve our understanding of functional properties. Subsequent sections explore structural and thermal properties of nests in more detail. The roles that a nest can play in maintaining nest humidity and in weather-proofing the contents are also explored. The concept that the nest is an extended phenotype that has a role in niche creation is explored before the review concludes with a consideration of future directions for research.

Despite its hyperarid climate, the Sahara Desert encompasses some large oases with extensive but rather fragile wetlands that are inhabited by Charadriforms. In this study we analyse the reproductive ecology of two species of Recurvirostridae, Black-winged Stilts Himantopus himantopus (more numerous) and Pied Avocets Recurvirostra avosetta (less numerous), nesting in an unstable habitat of the Saharan wetland of Chott Ain El Beida, Algeria, North Africa. The onset of egg laying was more stable and similar between years in Black-winged Stilts (15–19 April, on average, N = 315) than in Pied Avocets (13–21 April, on average, N = 73). Black-winged Stilts and Pied Avocets showed opposite yearly trends in egg laying dates. Clutches composed of 4 eggs dominated in both these species. They did not differ in hatching success of complete clutches (on average 73% and 77%, respectively). Average weights of eggs decreased from year to year during 2005–2007, suggesting that the individual quality of breeding birds decreased over the study years, probably corresponding with the progressive deterioration of the habitat. In the Black-winged Stilt, but not in the Pied Avocet, egg sizes decreased with the progress of the laying period. Another difference between egg-related aspects of the breeding ecology of these species was that only in Black-winged Stilts egg shape tended to affect hatching success of clutches, so that clutches of more elongated eggs had higher hatchability. To conclude, some aspects of breeding performance of waders may have a different form even in closely related species, depending on changing ecological conditions.

Several bird species show differential migration in relation to age and/or sex classes, often associated with morphological and behavioural differences. The Western Marsh Harrier Circus aeruginosus is a partial migrant, showing a strong sexual dimorphism in size. This species migrates on a broad front, undertaking long water crossings through the Mediterranean Sea. In this study we carried out a two-year survey on the pre-breeding migration of this species at three sites located in the Central Mediterranean region: the islands of Ustica and Panarea (Tyrrhenian Sea) and the Strait of Messina (Peloritani Mountains). The aim of this study was to analyse the flight strategies of this broad front migrant in relation to wind patterns, such as in relation to different sex and age classes. Our results revealed differential flight behaviours among harriers belonging to different sex classes, with adult females less attracted to islands than adult males during a sea crossing, and adult males reaching higher altitude early in the season along a mountain chain. It is suggested that adult males, thanks to their smaller size, use to a larger extent soaring flight by exploiting even weak thermals en route. Unlike the Tyrrhenian islands, few immatures were seen passing along the Peloritani Mountains, probably because they fly at lower altitudes over mainland, passing over areas where they can eventually find prey and/or rest at stop-over site en route. In conclusion, our study shows that the location of the observation post can affect the result concerning migration survey of both sex and age classes in this species, leading to evident bias.

The way an animal uses the home range and territory often vary in time according to its breeding state and habitat complexity. Adult dispersal can follow partner replacement, however little is known about seasonal/sex variation in partner replacement in tropical passerines. Here we tested if home range and territory size of the Rufous Hornero Furnarius rufus varies between the breeding and non-breeding seasons and if this variation is consistent across three distant populations in Brazil (UFJF, UnB, and MT). In addition, we described the frequency of partner replacements in relation to sex and breeding state in two of those populations (UFJF and UnB). We observed a decrease in 33% and 38% of home range size in the non-breeding season for two sites (UFJF and MT). Territory size decreased by 50% in the non-breeding season in UnB, but this could be due to a lower sampling effort during this season. Nevertheless, the home range expansion is consistent with a higher demand for resources during the breeding season. Home range sizes, but not sizes of territories, varied across sites. We also recorded 26 partner replacements, with no sign of sex or seasonal bias. Most replaced birds disappeared, suggesting that both sexes are under similar mortality risks, a usual main driver of partner replacement. Pair bonds lasted three or more years in 25% of the studied pairs. Altogether, these results provide insights for future studies on underlying mechanisms shaping home ranging, territoriality, and partner replacement in tropical birds that defend year-round territories.

Individual differences in cognition widely exist in diverse animal taxa. Such cognitive variance is supposed to be influenced by animal personality. While the relationships between various personality traits and performances in diverse cognitive tasks are not consistent, few studies have examined the effects of a particular personality trait on different cognitive abilities. We measured the exploratory behaviour of 35 individuals lab-reared Java Sparrows Lonchura oryzivora with a novel environment test and a novel object test. Three cognitive abilities of birds, for discrimination learning, reversal learning, and inhibitory control, were quantified in three classic cognition tasks (a colour association task, a colour reversal task, and a detour-reaching task). We found no correlation between the exploration and the trials required to pass the colour association task or the detour-reaching task. The slow explorers, however, needed less trials to reach the criterion in the colour reversal task. Our results suggest that slow explorers hold higher reversal learning ability. Slow-exploring style would be advantageous to birds when facing unpredictable environmental changes.

Birds defend territories by engaging in potentially costly behaviours, such as vocalizations and aggressive interactions. Songs are usually good proxies of individual quality, thus could help guarantee access and exclusivity to food, sexual partners and nesting sites. We described territorial and vocal behaviours of the Riverbank Warbler Myiothlypis rivularis, a year-round territorial wood-warbler (family Parulidae), and tested for relationships between territory size and individuals' vocal attributes. From October 2018 to April 2019, we banded 14 males and 9 females in the Atlantic Forest of south Brazil. We estimated territory sizes of nine pairs and recorded 10 and 5.4 h of 9 males and 6 females vocalizations, respectively. In male songs, a tradeoff between trill rate and frequency bandwidth indicates mechanical vocal constraints in the production of both parameters. Territory size did not relate to male song parameters, which could signal individual, rather than territorial, quality. However, females with broader bandwidth songs occupied smaller territories. Although the reduced sample size, which precludes generalization, this result may be a first indication of female song acting on territoriality in this species. Overall, this work presents new data on Riverbank Warbler and contributes to the knowledge on vocal tradeoffs in male songs and both male and female territorial behavior for wood-warblers. In addition, we highlight the need for further studies focused on female song, which like male song could be associated with territory defense.

In bird species with a lek mating system, male mating success is usually correlated with time spent at the lek, suggesting strong selection for lek attendance. We studied the lekking of Great Snipe Gallinago media males over 5 breeding seasons in Poland and found that, in apparent contradiction, 75% of males changed leks, often several times, within a single breeding season. GPS-tagged individuals tracked for an average of 31 days visited up to 9 different leks, often visiting 2–3 leks in quick succession within a few hours. Transitions between leks were entirely nocturnal, peaking before midnight. The majority of males that changed leks moved to sites within 50 km of the original lek, but 10% of males dispersed more than 100 km. Lek-switching males typically made several transitions between leks during the breeding season (median = 4), with most mobile birds changing display sites more than 20 times. Lek-switching probabilities showed seasonal variation, with no males changing leks early in the breeding season and frequent changes thereafter. The daily probability of lek change showed large inter-individual variation, allowing two groups of males to be distinguished, those who never or rarely changed leks (mean daily probability of lek change 0.02) and those who frequently changed leks (mean daily probability of lek change 0.23). This type of heterogeneity in male lekking behaviour is consistent with the hot-shot scenario of lek evolution. Here, lekking males with low mating chances should benefit from lek-switching — in contrast to top-ranking males — because changing display site may allow them to find leks with higher mating chances. Furthermore, regardless of its immediate success or failure, lek-switching can be seen as a form of prospecting behaviour that will pay off in future breeding seasons. Consistent with this, many of our lek-switching males moved in a way that suggests informed dispersal. The prevalence of intraseasonal lek switching in different Great Snipe populations across Europe should be assessed using the modern tracking devices, as this behaviour is likely to be much more widespread than reported in many previous studies.

Set aside fields act as potential nesting habitat and play an important role in nest success of ground nesters in farmlands. Asian countries utilize vast areas of their land as rice fields which along with adjoining habitats act as breeding ground for around 3% bird species in the Indian subcontinent. We investigated contribution of post harvested rice fields and associated habitats in nest success of three passerines within a tropical agricultural area. Nesting ecology of 90 pairs belonging to Oriental Skylark Alauda gulgula (n = 25 nests), Bengal Bush Lark Mirafra assamica (n = 32) and Paddyfield Pipit Anthus rufulus (n = 33) was studied from February 2016 to June 2017 in a complex of agricultural fields dominated by fallow stubble in the southern West Bengal, North East India. Nests were found in the stubble fields having uncut rice bases, adjacent cropped or uncropped other fields and levees. Location of the nests and their microhabitats seemed to be the most important factors concerning nesting habitat selection. Nest success was 48%, 34.4% and 21.2% in Skylark, Bush Lark and Pipit respectively. Model estimate of constant Daily Survival Rate (DSR) ranged between 0.90–0.95. Nest survival increased between 1–5% at rice bases for the three species. Pipit nests at rice bases showed 6.5% higher survival rate than open habitat. Nests at the open microhabitat had low nest survival irrespective of species. Model goodness of fit suggested that nest survival was affected mostly by combination of microhabitat and species variables. Results suggested that rice bases in post harvested fallow rice fields might play an important role in nest survival for passerines.

The reproductive ecology of the Andean Condor Vultur gryphus is poorly known. This note describes reproductive events of individual breeding pairs. We describe the minimum distances between nest sites, breeding success, elevation and the use of nesting cliffs of different breeding pairs of Andean Condors in the north-central Andes of Ecuador. We undertook 840 hours of observations of eight nesting events in areas on an elevational gradient from 2500 m to 4500 m during 2018 and 2019. Nesting events in Ecuador since 1996, were also reviewed which provided us a total of 21 breeding attempts at 16 nest sites. Minimum distances between the sites of breeding attempts were 25 m (since 1996) and 310 m (during the fieldwork). The nearest neighbour distance of Andean Condors simultaneously sharing the same cliff during partially overlapping breeding was 550 m and in different cliffs 2720 m. Breeding success was 0.75 and higher in reused nests. The results present previously unknown information that contributes to reproductive ecology and emphasizes the importance of the cliffs as critical areas for the conservation and permanence of the Andean Condor where management actions are urgent.