Influence of cave structure, microclimate and nest harvesting on the breeding of the White-nest Swiftlet Collocalia fuciphaga germani in Viêtnam

In Viêtnam, most White-nest Swiftlet Collocalia fuciphaga colonies (80% of the colonies in Da Nang and 58% in Khanh Hoa provinces), and all large ones, were found in caves with wide openings where the sea entered far inside and waves may wash away numbers of nests. In dry caves above sea level, air with a relative humidity below 70% may cause many nests to fall from the walls. Breeding success was strongly influenced by nest harvesting and was especially low in the third and fourth clutches. The best harvesting method is to collect the nests twice a year, and the first harvest should occur only when the first 10–15% of the nests have eggs. The second harvest should be made when second clutch fledglings have left the nest. The later the first harvest occurs, the lower are the ability of the swiftlets to rebuild second nests and the productivity of second clutches.     

New is not always better: low breeding success and different occupancy patterns in newly built nests of a long-lived species,the white stork Ciconia ciconia

Capsule An increase in new nest building in a white stork population revealed that they were built further from human settlement and on non-typical structures; such nests had lower breeding success resulting from later breeding.

Aim To determine why some birds build new nests rather than occupy older ones, and how new nests affect breeding performance compared to old nests, in a long-lived bird, the white stork.

Methods We compared new nest construction in 2010 with a long-term data set on white stork in Western Poland from 1974 to 2009. For data from 2010, we analysed nest location and breeding biology in detail.

Results Since 1974, the proportion of new build nests was ca. 1.6%; in 2010 this was 13.2%. Pairs in new nests bred later than pairs in old, and had smaller clutches and lower breeding success. New nests were located further from settlements and tended to be built on different structures. A significantly lower proportion of new nests were re-occupied in subsequent years.

Conclusions Pairs may build new nests to gain experience in nest building, cooperation and foraging for subsequent seasons or because of competitive pressure when the environment is close to carrying capacity. Breeding success can be initially very low.     

Regulation of Activity in Desert-Living Striped Mice: The Importance of Basking

Deserts represent challenging, energy restricted environments for small mammals, but offer ample exposure to sunlight that might be used for energy saving during basking. The Succulent Karoo desert in southern Africa is a seasonal environment with cold moist winters, followed by maximum food availability in spring and dry hot summers with food shortage. The striped mouse (Rhabdomys pumilio) from the Succulent Karoo desert is diurnal and its activity is influenced by photoperiod in captivity. However, in contrast to standardized laboratory conditions, it can be expected that several factors other than photoperiod influence its activity pattern in the field. We expected that striped mice behave in a way that indicates that they use basking to passively warm up and thus reduce endogenous energy expenditure. We studied activity and basking patterns in 56 social groups of striped mice for a period of 4 yr, comprising 1534 observation sessions at their nests. Mice generally started activity around the time the sun illuminated their nest and terminated activity when their nest was no longer sunlit, i.e. they were strictly diurnal. The onset of activity was delayed on days when ambient temperature was colder and when group sizes were smaller. During the breeding season when food availability was high, striped mice usually left the nest before it was sunlit without basking. Outside the breeding season, they emerged and basked in front of nests mainly after nests were sunlit. These findings concur with the view that striped mice trade‐off between active energy gain via foraging and passive energy acquisition by sun basking.     

Buildings promote higher incubation temperatures and reduce nest attentiveness in a Neotropical thrush

Incubation is an energetically costly parental task of breeding birds. Incubating parents respond to environmental variation and nest‐site features to adjust the balance between the time spent incubating (i.e. nest attentiveness) and foraging to supply their own needs. Non‐natural nesting substrates such as human buildings impose new environmental contexts that may affect time allocation of incubating birds but this topic remains little studied. Here, we tested whether nesting substrate type (buildings vs. trees) affects the temperature inside the incubation chamber (hereafter ‘nest temperature’) in the Pale‐breasted Thrush Turdus leucomelas, either during ‘day’ (with incubation recesses) or ‘night’ periods (representing uninterrupted female presence at the nest). We also tested whether nesting substrate type affects the incubation time budget using air temperature and the day of the incubation cycle as covariates. Nest temperature, when controlled for microhabitat temperature, was higher at night and in nests in buildings but did not differ between daytime and night for nests in buildings, indicating that buildings partially compensate for incubation recesses by females with regard to nest temperature stability. Females from nests placed in buildings exhibited lower nest attentiveness (the overall percentage of time spent incubating) and had longer bouts off the nest. Higher air temperatures were significantly correlated with shorter bouts on the nest and longer bouts off the nest, but without affecting nest attentiveness. We suggest that the longer bouts off the nest taken by females of nests in buildings is a consequence of higher nest temperatures promoted by man‐made structures around these nests. Use of buildings as nesting substrate may therefore increase parental fitness due to a relaxed incubation budget, and potentially drive the evolution of incubation behaviour in certain urban bird populations.     

The functional significance of multiple nest-building in the Australian Reed Warbler Acrocephalus australis

The vast majority of bird species build a nest in which to breed. Some species build more than one nest, but the function of most multiple nest-building remains unclear. Here we describe the unusual nest-building behaviour of the Australian Reed Warbler Acrocephalus australis , and test experimentally the hypotheses that multiple nest-building is related to individual condition or territory quality, and plays a role in mate assessment. Australian Reed Warblers built two types of nest structures: 'type I' nests, which were used for eggs and nestlings, and 'type II' nests, which were structurally distinct from type I nests, did not support eggs, nestlings or adults and were not essential for successful breeding. The number of type II nests built in each territory varied. Type II nests were only built before breeding had commenced in a territory and females were not observed participating in their construction, supporting a role in female mate choice. Birds provided with supplementary food built significantly more type II nests than control birds. However, supplementary-fed birds did not have greater pairing success, and the addition of further type II nests to territories did not increase the pairing rate or type II nest construction in those territories. There was no relationship between the presence of type II nests and either reproductive success or likelihood of nest predation. We discuss the implications of these results in light of previous suggestions regarding the function of multiple nest-building in birds.     

Bats in bird nests in Australia: a review

Bats (Microchiroptera) utilize few types of bird nests as roosts. Ten species of bats (Molossidae and Vespertilionidae) were recorded roosting in the enclosed bottle-shaped mud nests of the Fairy Martin Hirundo ariel; two species (Vespertilionidae) were located in the hanging nests of scrubwrens Sericornis spp. and the Brown Gerygone Gerygone mouki; two species (Vespertilionidae) in the enclosed plant material nests of the Grey-crowned Babbler Pomatostomus temporalis and Fernwren Oreoscopus gutturalis; and one species (Emballonuridae) was recorded in the open cup-shaped nest of the White-rumped Swiftlet Collocalia spodiopygius. No information was available on the importance of bird nests as breeding sites and only one species, the Chocolate Wattled Bat Chalinolobus morio, has been recorded hibernating in a nest. Bird nests in Australia provide roosting habitat for four threatened bats and may be important to the conservation of these species.     

Factors associated with nest survival of Black‐throated Sparrows,desert‐breeding nest‐site generalists

Black‐throated Sparrows (Amphispiza bilineata) are common breeding birds throughout the desert regions of North America and can be considered nest‐site generalists. Information about how spatial (e.g., vegetation) and temporal factors influence nest survival of these sparrows is lacking throughout their range. Our objective was to examine the spatial and temporal factors associated with nest survival of Black‐throated Sparrows at the nest and nest‐patch scales in the predator‐rich environment of the northern Chihuahuan Desert of New Mexico. We used a logistic‐exposure model fit within a Bayesian framework to model the daily survival probability of Black‐throated Sparrow nests. Predation was the leading cause of nest failure, accounting for 86% of failed nests. We found evidence of negative associations between nest survival and both vegetative cover above nests and shrub density within 5 m of nests. We found no support for other habitat covariates, but did find strong evidence that daily survival rate was higher earlier in the breeding season and during the egg‐laying stage. A decline in nest survival later in the breeding period may be due to increased predator activity due to warmer ambient temperatures, whereas lower survival during the incubation and nestling stages could be a result of increased activity at nests. A generalist approach to nest‐site selection may be an adaptive response to the presence of a diverse assemblage of nest predators that results in the reduced influence of spatial factors on nest survival for Black‐throated Sparrows.     

Nest demographics and foraging behavior of <Emphasis Type="Italic">Apterostigma collare</Emphasis> Emery (Hymenoptera,Formicidae) provide evidence of colony independence

Apterostigma collare Emery is a highly derived fungus-growing ant within the Tribe Attini whose small, fungal nests are found in tropical rain forests. This study focuses on determining the colony structure of A. collare, specifically searching for evidence of polydomy or independence. We surveyed and observed nests in the field, and performed foraging bioassays and dissected nests in the laboratory. We determined the size and contents of nests in field populations. Nests found near other nests were not statistically different in size compared to nests found alone. There was also no statistical difference between near and lone nests regarding the presence of a queen in the nest. Most nests contained one queen with brood and workers, regardless of their proximity to other nests. Observations also were made of foraging and trail-marking behaviors. Foraging activity observed in the field revealed that workers left the nest area and followed trails upwards into the canopy, but they did not interact with foragers from other nearby nests. In a laboratory foraging arena, foragers marked a trail to a food source by dragging the gaster. Bioassays showed that A. collare workers preferred their own foraging trails, but not those of other conspecific colonies. All results suggest that each nest represents an independent colony, supporting a previous report that nests found in close proximity do not constitute a polydomous colony. Received 19 July 2006; revised 23 March 2007; accepted 6 June 2007.     

Predation risk affects trade-off between nest guarding and foraging in Seychelles warblers

The fitness costs of egg loss for Seychelles warblers (Acrocephalus sechellensis)on Cousin Island are considerable because warblers have a single-eggclutch and no time to lay a successful replacement clutch. Onthe islands of Cousin and Cousine, with equal densities of Seychellesfodies (Foudia sechellarum), nearly 75% of artificial eggs placedin artificial nests were predated by fodies after 3 days. OnAride Island with no fodies present, loss of artificial eggswas not observed. Female warblers incubate the clutch, and malewarblers guard the clutch when females are absent. Deterrenceof fodies by male warblers is efficient: loss rate of eggs fromunattended warbler nests was seven times as high as from attendednests, and the more nest guarding, the lower the egg loss andthe higher the hatching success. Egg loss is independent ofthe amount of incubation by females. There is no trade-off betweenincubating and foraging by females. Nest guarding competes withforaging by males, and this trade-off has a more pronounced effecton egg loss when food availability is low. The transfer of breeding pairsfrom Cousin to either Cousine with egg-predating fodies or toAride without fodies allowed us to experimentally investigatethe presumed trade-off between nest guarding and foraging. OnCousine, individual males spent the same amount of time nestguarding and foraging as on Cousin, and egg loss was similarand inversely related to time spent nest guarding as on Cousin.Males that guarded their clutch on Cousin did not guard theclutch on Aride but allocated significantly more time to foragingand gained better body condition. Loss of warbler eggs on Aridewas not observed. Time allocation to incubating and foragingby individual females before and after both translocations remainedthe same.     

Nest reuse in arctic‐breeding shorebirds: an analysis of potential benefits and factors affecting the occurrence of this rare behavior

During a 13‐yr study near Utqia?vik (formerly Barrow), Alaska, we documented the prevalence of nest reuse in eight arctic‐breeding shorebirds. We evaluated whether nest reuse saved individuals time and energy, enhanced nest survival, or was related to nest density. We documented 208 (6.2%) cases of nest reuse among 3336 nesting attempts. Nest reuse occurred in all years but the first and in all species, with greatest reuse in semipalmated sandpiper (10.9%) and American golden‐plover (10.0%). While most cases of nest reuse occurred with conspecifics, many cases of heterospecific nest reuse were also observed, indicating high niche overlap in nest site preferences among species. We found that individuals reusing old nests may have benefited by nesting earlier, but nest reuse did not generally enhance nest survival. A significant positive relationship was also found between nest reuse and nest density at the community level and for four of the eight species, suggesting high inter‐ or intraspecific competition combined with limited suitable nest sites may force individuals to reuse old nests. Our observations also suggest that upland nesting species may be the most dependent on old nest sites. Preferential development of these sites may therefore have a previously unknown detrimental effect on these species, although further study is needed to better determine the impact of such habitat loss.     

Testing hypotheses about the function of repeated nest abandonment as a life history strategy in a passerine bird

Nest structures are essential for successful reproduction in most bird species. Nest construction costs time and energy, and most bird species typically build one nest per breeding attempt. Some species, however, build more than one nest, and the reason for this behaviour is often unclear. In the Grey Fantail Rhipidura albiscapa, nest abandonment before egg‐laying is very common. Fantails will build up to seven nests within a breeding season, and pairs abandon up to 71% of their nests before egg‐laying. We describe multiple nest‐building behaviour in the Grey Fantail and test four hypotheses explaining nest abandonment in this species: cryptic depredation, destruction of nests during storm events, and two anti‐predatory responses (construction of decoy nests to confuse predators, and increasing concealment to ‘hide’ nests more effectively). We found support for only one hypothesis – that abandonment is related to nest concealment. Abandoned nests were significantly less concealed than nests that received eggs. Most abandoned nests were not completely built and none received eggs, thus ruling out cryptic predation. Nests were not more likely to be abandoned following storm events. The decoy nest hypothesis was refuted as abandoned nests were constructed at any point during the breeding season and some nests were dismantled and the material used to build the subsequent nest. Thus, Grey Fantails are flexible about nest‐site locations during the nest‐building phase and readily abandon nest locations if they are found to have deficient security.     

Digging effort in leaf-cutting ant queens (<Emphasis Type="Italic">Atta sexdens rubropilosa</Emphasis>) and its effects on survival and colony growth during the claustral phase

Nest foundation in the leaf-cutting ant Atta sexdens is claustral, and the single queen completely relies on its body reserves throughout, approximately, 9 weeks until the first workers emerge and initiate foraging. Nest digging is much time- and energy-consuming, and it is an open question how queens decide on the length of the tunnel they dig and therefore the depth of the initial chamber. Shallow founding nests may be energetically cheaper to dig, but queens may be more exposed to changing environmental variables. Deeper nests, on the other hand, may be climatically more stable and suitable, but more expensive to dig. We hypothesized that the maximal nest depth excavated by Atta founding queens may represent the outcome of an evolutionary trade-off between maximizing nest depth and minimizing energy expenditure during digging, so as to save energy for the long claustral phase. We tested this hypothesis by comparing the fitness consequences of increased digging effort in queens that were experimentally stimulated to excavate a complete founding nest either once, twice or three times consecutively compared to control queens that did not dig. Fitness was quantified as mortality rates, rates of egg-laying and offspring production, and size of the fungus garden until the emergence of the first workers. Results showed that, in contrast with the initial expectations, fungus growth, egg-laying rates and offspring production were not affected by the increased digging effort in the experimentally induced successive excavations. However, a significant higher mortality was observed in queens with increased digging effort, i.e., those that dug two or three nests consecutively. It is argued that in queens a behavioral mechanism for the control of nest depth has evolutionary been selected for as a trade-off between maximizing nest depth, to favor protection of the queen against unsuitable environmental variables, and minimizing energy expenditure during digging, which significantly affects survival.     

Breeding dispersal of Northern Flickers Colaptes auratus in relation to natural nest predation and experimentally increased perception of predation risk

After nest predation, breeding dispersal can be an effective strategy to avoid local nest predators. Furthermore, encounters with predators at a nest during the pre-laying stage may be used by parents to judge future risk, such that they may abandon a nest when a nest predator has been encountered. We studied whether the between- and within-year breeding dispersal of Northern Flickers Colaptes auratus was dependent upon the outcome of the previous nesting attempt. We also tested whether pairs presented with a model predator prior to egg-laying were more likely to abandon their nests than were pairs presented with a control model. Between years, males moved significantly further after having their nest depredated than did successful males, and females showed the same trend. However, these movements did not result in greater reproductive success. More pairs switched sites within years after having their nest depredated, but those that remained and those that moved had equal subsequent nest success. Stressful encounters with predators involving nest defence may trigger dispersal both between and within years, although reproductive benefits are unclear. The proportion of pairs abandoning nests did not differ between parents presented with control or predator models, suggesting that a single encounter with a predator is not a sufficient deterrent against continued use of a particular nest.     

Landscape and anti-predation determinants of nest-site selection, nest distribution and productivity in a Mediterranean population of Long-eared Owls Asio otus

Nest predation is an important determinant of owl breeding success. We studied Long-eared Owl Asio otus productivity and attributes of nest-sites at the microhabitat and landscape scales in a Mediterranean locality over an 8-year period. We examined the effect on nest location and productivity of protective cover in concealing the nest from aerial and terrestrial predators. A dense cover of ivy and tree-foliage at canopy level favoured nest location but not productivity. By contrast, high shrub cover beneath the nest was selected by Owls and was positively related to both the site reoccupancy rate and the overall number of young fledged. Pre-fledging Owls use the ground, where they are exposed to terrestrial predators, which are much more abundant in the study area than are aerial predators. Our results therefore support the hypothesis that Owls adapt nest-site choice to local sources of predation risk. As reported elsewhere, Long-eared Owls in our study area showed restricted territoriality and nested in clusters. As active nest-sites during the same breeding season were more than 1 km apart on average, and their productivity was never greater for clustered nests than for more isolated nests, nest aggregation could not be interpreted as a case of facultative colonial breeding, which has been reported for this species in other areas. Neither landscape variables indicative of the availability of foraging areas nor structural attributes that protect young from predators explained the remarkable scarcity of nests in half of the study area. Unmeasured factors such as human disturbance could explain the pattern of distribution of Long-eared Owl nests.     

Ecological constraints on independent nesting in facultatively eusocial hover wasps

Recent field experiments suggest that cooperative breeding in vertebrates can be driven by a shortage of breeding territories. We did analogous experiments on facultatively eusocial hover wasps (Stenogastrinae: Liostenogaster flavolineata). We provided nesting opportunities by removing residents from 39 nests within a large aggregation (1995), and by glueing 20 nests obtained from a distant site into a second aggregation (1996). We prevented nest-less floaters from competing for these opportunities in 1995 but not in 1996. In both years, helpers in unmanipulated groups were given opportunities to nest independently without having to incur nest-building costs and with a reduced wait before potential helpers emerged. Helpers visited the nests we provided, but adopted only a small proportion (5% of 111 vacancies created in 1995). Others were adopted by floaters, but a significant proportion of nests were never adopted (nine out of 20 in 1995, seven out of 20 in 1996). Helpers that visited nests did not originate from particular kinds of social group. Nests containing older brood were more likely to be adopted, and adopting females rarely destroyed older brood. A general feature of social insect but not vertebrate life-histories, the long period of offspring dependency relative to the short life expectancy of adult carers, may be a key factor constraining independent nesting.     

Behavioural ecology of the North Sulawesi Tarictic Hornbill Penelopides exarhatus exarhatus during the breeding season

Two nests of the North Sulawesi Tarictic Hornbill Penelopides exarhatus exarhatus were monitored for one breeding season (April-July). The females sealed themselves into the nest cavities and remained there for 70–90 days. Incubation was estimated at 16–19 days, and at both nests two offspring fledged. Tarictic Hornbills are cooperative breeders with up to three helpers at the nest and defend foraging territories of 72–139 ha. Food items delivered to the nest included fruits of 34 species (85% of diet items) and invertebrates. Provisioning by helpers allowed breeding males to reduce investment in parental care and may accelerate the development rates in chicks. Constraints on dispersal probably result from habitat saturation rather than living in an unpredictable environment.     

Stage-dependent foraging in breeding black-legged kittiwakes Rissa tridactyla: distinguishing behavioural responses to intrinsic and extrinsic factors

Different phases of the annual cycle in birds and mammals are often associated with characteristic and recurrent foraging behaviours. The extent to which stage‐dependent changes in foraging behaviour are caused by intrinsic or extrinsic factors is unclear. We controlled for the effects of extrinsic factors by synchronising groups of incubating and chick‐rearing black‐legged kittiwakes Rissa tridactyla. Synchrony amongst incubators and rearers was achieved experimentally by switching eggs between nests. Behavioural responses to the treatment varied between the sexes. Male kittiwakes with prolonged‐incubation made fewer foraging trips but of greater duration compared to those rearing chicks resulting in no change in the time spent on trips between the two groups. Females with prolonged‐incubation carried out fewer trips than those rearing chicks but trip duration did not differ between the two stages which resulted in prolonged‐incubating birds spending a lower percentage time on trips. In contrast, foraging ranges did not differ between prolonged‐incubation and chick‐rearing birds for either sex. This suggests that extrinsic factors, such as food availability and distribution determine kittiwake foraging locations and ranges, whereas intrinsic factors, reflected in parental duties, constrain nest attendance. Female prolonged‐incubators invested lower levels of parental effort, in terms of daily energy expenditure, compared to chick‐rearers whereas males did not show stage‐related differences in energy expenditure. This provides evidence that incubation could be an energetically cheaper stage although under normal conditions this difference may be masked by temporal variation in environmental factors. We conclude that while conditions differ between the incubation and chick rearing stages for kittiwakes at this colony, they are not the main factors prompting changes in stage‐related foraging patterns. Intrinsic factors such as sex differences, or behaviours required for each stage of the annual cycle, rather than extrinsic factors related to seasonal environments, are likely to be the main proximate cause of recurring changes in behaviour between breeding stages.     

Intraspecific parasitism and nest defence in the solitary pompilid wasp Anoplius viaticus (Hymenoptera: Pompilidae)

The nesting behaviour of individually marked female pompilid wasps, Anoplius viaticus , was observed at a Breckland heath site with particular emphasis on intraspecific parasitism and nest defence. Prey was stolen from conspecifics while it was being carried to the nest site, and while it was left unattended during nest construction. Females also appeared to brood parasitize each other's completed nests. Parasitism appeared to be opportunistic. Brood parasitism may be a tactic by which time-limited females can increase their fecundity. By placing prey in vegetation tufts during nest construction, females may reduce the risk of prey theft. An individual female's successive unicellular nests were clustered and therefore easier to defend, in many ways resembling a multicellular nest. Females defended their clusters vigorously, visiting them every few minutes during foraging and expelling conspecifics from the vicinity. This type of nest defence may be costly, and has rarely been observed in solitary wasps.     

Fear factor: prey habitat selection and its consequences in a predation risk landscape

Predation risk influences prey use of space. However, little is known about how predation risk influences breeding habitat selection and the fitness consequences of these decisions. The nest sites of central-place foraging predators may spatially anchor predation risk in the landscape. We explored how the spatial dispersion of avian predator nests influenced prey territory location and fitness related measures. We placed 249 nest boxes for migrant pied flycatchers Ficedula hypoleuca , at distances between 10 and 630 m, around seven different sparrowhawk nests Accipiter nisus . After closely monitoring flycatcher nests we found that flycatcher arrival dates, nest box occupation rates and clutch size showed a unimodal relationship with distance from sparrowhawk nests. This relationship suggested an optimal territory location at intermediate distances between 330 and 430 m from sparrowhawk nests. Furthermore, pied flycatcher nestling quantity and quality increased linearly with distance from sparrowhawk nests. These fitness related measures were between 4 and 26% larger in flycatcher nestlings raised far from, relative to those raised nearby, sparrowhawk nests. Our results suggest that breeding sparrowhawk affected both flycatcher habitat selection and reproductive success. We propose that nesting predators create predictable spatial variation in predation risk for both adult prey and possibly their nests, to which prey individuals are able to adaptively respond. Recognising predictable spatial variation in perceived predation risk may be fundamental for a proper understanding of predator-prey interactions and indeed prey species interactions.     

Building multiple nests is associated with reduced breeding performance in a south temperate population of Grass Wrens Cistothorus platensis platensis

Grass Wrens Cistothorus platensis build two types of non-breeding nest structures: platforms and dummy nests. Platforms are rudimentary accumulations of grasses concealed between vegetation. Dummy and breeding nests are dome-shaped with a similar structural layer. We used a nest-removal experiment and observational data to evaluate several hypotheses regarding the adaptive significance of building multiple nests in a south temperate population of Grass Wrens. Building non-breeding nests was not a strategy of males to attract additional females, as most of these nests were built after pair formation and both sexes collaborated during building. Building non-breeding nests was not a post-pairing display as the presence of multiple nests did not increase female investment in the breeding attempt: clutch size and female provisioning to nestlings did not differ between experimental and control territories where no non-breeding nests were removed. Similarly, in non-manipulated territories, clutch size and female provisioning were not correlated with the number of non-breeding nests or with males’ nest-building effort. Contrary to this hypothesis, the number of non-breeding nests was associated with delayed clutch initiation and reduced hatching success. The presence of non-breeding nests did not reduce nest predation and brood parasitism, which did not differ between experimental and control territories. We did not detect differences in concealment between non-breeding and breeding nests, suggesting that non-breeding nests were not the result of abandonment before egg-laying to reduce subsequent nest predation. Dummy nests did not provide shelter; they were not used frequently for roosting over the breeding season and were not maintained during the non-breeding season. We suggest that building non-breeding nests may be an attempt by males to manipulate the decision of females to breed with a mate they might otherwise reject or to start reproduction earlier than optimal for the females.