Avian Biology Research

Nest placement affects the risk of predation and determines the microclimate for incubation. We have analysed the nest placement of the blackbird nests and the temperatures at which they are exposed in an orange plantation from Eastern Spain. The data come from a 16.9 ha of an orange plantation. In this plot, nest searching techniques were applied. Nest placement and the temperatures at midday were recorded from a sample of 84 nests. Furthermore, a sample of 16 nests was used to determine the daily variation between 8:00 and 20:00 hours. We measured the nest height, tree height, and distance from the tree centre to the nest, and the length of the longest branch. The temperatures inside the nest cup and of the surrounding air temperatures were also obtained. The range of the orange tree height was 82-425 cm (mean = 234.0 cm). The length range of the longest branch was 11-311 cm (mean = 136.4). The nests were placed at heights between 41 and 223 cm (mean = 134.4) and the distance from the centre of the tree varied from 8 to 233 (mean = 126.5). There was no variation in the nest heights and distances from the trunk to the nest place as the breeding season progresses. The air temperature (T_at) and the nest temperature (T_ict) at midday increases as the breeding season progresses but the difference between T_at and T_ict did not vary according to the time in the breeding season. The daily difference between the air and the nest temperatures increased from 08:00h to 12:00h and then decreased. Only three nests out of the 100 nests sampled were successful inbreeding.

The Ethiopian Bush-crow is an endemic Ethiopian bird species which has a very small and climatically distinct range that is cooler, dryer and more seasonal than the surrounding areas. Bush-crows build large domed nests made of thorny twigs with comparatively thick walls and a soil-lined bottom. In our preliminary study, we studied the thermal properties of a bush-crow nest with the aid of IR thermography. Our results show that there was no heat emission in the early morning and that nest surface temperatures clearly corresponded to the temperature changes during the day. Therefore we hypothesise that the nest construction provides substantial thermal insulation during the night time and presumably also delays temperature increase in the internal nesting chamber during the day time. We suggest that the bush-crow's specific nest construction may have contributed to its persistence under the climatically unique south Ethiopian conditions.

Recent studies are documenting the extent to which the mass and construction of bird nests varies between individuals and locations. In the Blue Tit (Cyanistes caeruleus) and Great Tit (Parus major), temperatures experienced by females during nest construction are inversely related to nest mass. Moreover, Mainwaring et al. (Journal of Biogeography, 2012) showed that nests constructed at high latitude are heavier and better insulated than nests built by conspecifics in the south. Although mean spring temperature was used as a proxy for latitude in the Mainwaring et al. study, it remains untested whether individual birds build nests in response to a narrower range of temperatures experienced at the start of the breeding season. Our study showed that irrespective of latitude nest mass, and in particular nest cup mass, of Blue Tits and Great Tits was significantly affected by the temperature experienced by the birds for the seven days preceding clutch initiation. Similar results were seen with the insulatory properties of nests. The potential impact of variation in nest construction and insulation on subsequent incubation and chick-rearing behaviour is discussed.

The Lesser Kestrel is a facultative colonial raptor mostly breeding in man-made structures. During 2009-2011 we checked the fate of 545 nests found in 18 colonies located in south-eastern Sicily. We determined the reproductive success of breeding pairs by analysing the survival time of each egg to hatching (n = 2,495) and each nestling to fledging (n = 1,849) with the linear hazard model of survival times. We determined whether egg and nestling survival differed between years with a Gehan–Wilcoxon test. By Cox regressions, we related the survival times with nest and colony features. Egg and nestling survival times showed a strong annual effect. The two reproductive stages of the Lesser Kestrel, when controlled for the annual effect, demonstrated a significant effect for some nest and colony features. Most of them, like the height from the ground, nest depth, reused nests and the presence of Jackdaws, are likely to be related to the predation pressure faced by Lesser Kestrel nests. Westward and southward nests had a better egg survival with respect to those on the cold sides and in the interior of buildings. The location of colony on the agricultural plain and human disturbance ranked as the most important variables, with core location of a colony and high disturbance levels negatively affecting the reproductive success of the Lesser Kestrel in the Gela Plain, so urging a more environmentally aware land use management of this Important Bird Area.

Nests are built by nearly all bird species and can be extremely varied in their structural characteristics, both within and among species. As with a number of other avian behaviours, it seems plausible that early learning might be important in producing adult nest-building behaviour. To examine whether preferences that adults have for nest materials are related to their early-life experience, we experimentally manipulated the colour of the nest in which Zebra Finch pairs built and raised chicks. We then tested these chicks at maturity to determine whether they preferred the colour of the nest from which they had fledged or preferred the same colour as their father. We also examined the overall structure of nests that fathers and their sons built to determine whether the nest a male builds resembles that from which he hatched. When males and females naïve to building were paired as adults and tested for their nest material preferences, they did not prefer the colour of their natal nest. When these males were re-paired and their preference tested a second time, the majority then preferred the colour that their father had preferred (which was also the colour preferred by most of the males). The structural components of a male's nest did not resemble the nest built by his father, but neither did his father's nests resemble each other. We found no evidence that the experience of the nest from which a bird fledges influences his preferences for the colour of nest material or the structure of his first nest.

We studied the nesting biology of the Syrian woodpecker (Dendrocopos syriacus) in Israel, emphasising its physiological aspects and the environment of the tree hole nest cavity (~ 2 litres in volume). Eggs (mean mass = 5.4 ± 0.4 g SD) are laid once a day during April and May to produce a mean clutch size of four (range 3-5). Active incubation starts after the last egg is laid and lasts 11 days. Both hatching and fledging are spread over 2-3 days. Parents share incubation during the day but only males incubate at night. Both parents share the feeding of the nestlings equally. Males occupy and guard the empty nest at night all year round. Incubation and fledging periods add up to a normal fledging time for the species. The young are fed by their parents outside the nest for another month.

Mean egg temperature was not significantly different between day and night, averaging 34.2°C (± 4.3 SD). Mean egg water loss was 1.4 % d⁻¹ of the initial egg mass prior to the onset of incubation and 0.5% d⁻¹ during incubation. The extrapolated total water loss of the eggs was 13.1% at the end of incubation. This indicates a good match of cavity humidity and the water vapour eggshell conductance of 1 mg·(d Torr)⁻¹ (=100 mg·(d kPa)⁻¹), where, in spite of the higher egg temperature during active incubation, the egg water loss rate is reduced due to the presence of the incubating parent.

Gas composition at the bottom of the nest initially decreased by ~ 1.75 % for O₂ whereas CO₂ increased by ~ 1.20 %, due to clutch activities until the nestlings were about 15 days old. There was little change in nest gas composition between 15 and 22 days of rearing. From that time on until fledging O₂ concentration increased and CO₂ decreased due to nestlings’ up and down activity in the nest shaft and the fact that they fledge asynchronously at the age of 26 days.

Birds may signal their condition, health or parental disposition to mates through large nests or intense or elaborate nest-building. The mass, number or elaborateness of nests may exceed their strict reproductive requirements. In several species, courtship rituals include exhibition of nesting materials to mates, and some nests are not used for breeding. Signalling through nests or nest construction may occur both before and after mating and may involve either males or females. Only males appear to be involved in pre-mating signalling, while both males and females may signal after mating. In several species, nest size and nest building activity has been associated with the condition of nest-building males, and females in some cases, while the evidence for parental disposition has been more mixed. Nest defence capacity has also been associated with nest size. In some species, males attract more mates through construction of multiple nests not related to breeding. The benefits obtained by males after pairing through differential allocation of their mates have been found in several species in terms of larger clutches, earlier hatching, biased sex ratios and increased parental investment. There is less evidence of this type of benefits for females. Measured responses of assumed receivers of the information provided by active nest construction may positively affect their fitness. Predators are probably attracted to bulky nests and so nest predation may have selected for concealed nests and for inconspicuous nest building activities, which has probably limited exaggeration of nest-building signals. There is also some evidence that ectoparasites and brood parasites may be attracted to bulky nests. Although signalling through nest construction appears as a plausible evolutionary scenario, much more empirical work needs to be done to demonstrate the relevance of nest-building signals.

Cleaning passerine nestboxes after birds have fledged is widely thought to remove parasites such as fleas. Experiments are now described that examine the value of cleaning such nests after use.