Advancing breeding phenology does not affect incubation schedules in chestnut‐crowned babblers: Opposing effects of temperature and wind

Projecting population responses to climate change requires an understanding of climatic impacts on key components of reproduction. Here, we investigate the associations among breeding phenology, climate and incubation schedules in the chestnut‐crowned babbler (Pomatostomus ruficeps), a 50 g passerine with female‐only, intermittent incubation that typically breeds from late winter (July) to early summer (November). During daylight hours, breeding females spent an average of 33 min on the nest incubating (hereafter on‐bouts) followed by 24‐min foraging (hereafter off‐bouts), leading to an average daytime nest attentiveness of 60%. Nest attentiveness was 25% shorter than expected from allometric calculations, largely because off‐bout durations were double the expected value for a species with 16 g clutches (4 eggs × 4 g/egg). On‐bout durations and daily attentiveness were both negatively related to ambient temperature, presumably because increasing temperatures allowed more time to be allocated to foraging with reduced detriment to egg cooling. By contrast, on‐bout durations were positively associated with wind speed, in this case because increasing wind speed exacerbated egg cooling during off‐bouts. Despite an average temperature change of 12°C across the breeding season, breeding phenology had no effect on incubation schedules. This surprising result arose because of a positive relationship between temperature and wind speed across the breeding season: Any benefit of increasing temperatures was canceled by apparently detrimental consequences of increasing wind speed on egg cooling. Our results indicate that a greater appreciation for the associations among climatic variables and their independent effects on reproductive investment are necessary to understand the effects of changing climates on breeding phenology.     

Experimental evaluation of nest shelter effects on weight loss in incubating common eiders Somateria mollissima

Evaluating consequences of habitat selection is an important step in understanding life history strategies and behavioural decisions of animals. Kilpi and Lindström (1997) found that incubating common eiders Somateria mollissima on exposed, treeless islands lost weight faster than females nesting on wooded islands and proposed that this difference was due to adverse incubation conditions at exposed nests. Therefore, we tested whether common eiders gained an advantage when nesting in sheltered habitats by placing artificial shelters over randomly-selected females after the onset of incubation within an eider colony in arctic Canada. We predicted that sheltered females would be heavier on completion of incubation than control hens lacking shelters. Females nesting in artificial shelters experienced a more moderate thermal environment at both cold and warm temperature extremes. Eiders nesting in shelters were heavier than control females during mid incubation, consistent with habitat-specific rates of weight loss reported by Kilpi and Lindström (1997) . Natural overhead cover was available at potential nests but few eiders used those sites. We suspect that microclimatic advantages offered by sheltered sites may be offset by costs of increased female vulnerability to predators. Further work is needed to test this hypothesis, and to determine mechanisms responsible for lower weight loss in eiders attending well concealed nests.     

Refuge size preference in the field cricket Gryllus bimaculatus

Size preference for artificial refuges was examined in the adult field cricket Gryllus bimaculatus under laboratory conditions. Blinded crickets were placed individually in a container consisting of a circular arena and six different-sized artificial refuges (triangular tent-like shelters). The crickets were allowed to walk freely inside the container for a constant period. Size preference was evaluated by determining cumulative stay period in each shelter. When the depth of the shelters varied from 60 to 160 mm at 20-mm intervals, and the width was fixed at 30 mm, both males and females tended to remain in relatively longer shelters (≥ 140 mm). Females, in particular, exhibited a distinct preference for the longest shelter (160 mm). The width of the shelters was then varied from 20 to 40 mm at 4-mm intervals, and the depth was fixed at 100 mm. Although males did not show selectivity to specific shelters, females tended to select a shelter with a particular width (32 mm). These results suggest that adults of G. bimaculatus have size preferences for refuges under blinded conditions. However, the preferences may involve sexual differences as well.     

Experimental reduction of incubation temperature affects both nestling and adult blue tits Cyanistes caeruleus

Incubation was for a long time considered to be a period of decreased activity and low cost for parents. It was therefore ignored as a potential factor affecting life‐history trade‐offs in birds. Lately this view has started to change, and studies now show that there might be considerable costs connected to incubation. We experimentally reduced the nest temperature during incubation in blue tits Cyanistes caeruleus, thus increasing the energetic cost of incubation, to test the importance of incubation as a component of reproductive costs and for nestling quality. While most other studies use brood size manipulation to manipulate reproductive costs, we were able to separate treatment effects acting during the incubation period from those acting on later reproductive performance by applying a cross‐foster design. We were also able to isolate the effects of decreased incubation temperature on the nestlings from treatment effects acting on incubating females. We found no experimental effect on the length of the incubation period or on hatching success. The lower temperature during incubation, however, caused lower growth rates in nestlings and reduced chick rearing capacity in adults. We conclude that incubation is a costly period, with the potential to affect both the trade‐off between current and future reproduction and the one between parental effort and offspring quality within the current breeding attempt.     

Roles for structural and temporal shelter-changing by fern-feeding lepidopteran larvae

Summary Larvae of the pyralid moth, Herpetogramma aeglealis, construct feeding shelters upon the Christmas fern (Polystichum acrostichoides). Field and laboratory study involving 532 shelters showed that as the larvae mature, they sequentially inhabit approximately 5 shelters of 3 distinct types, constructed at night on different fronds of the same plant. The bundle shelter, simple and ephemeral, is first to be inhabited and constructed. The fiddlehead shelter which houses slightly older larvae strongly resembles contemporaneously emerging frond fiddleheads. The final shelter form, the globe, is a silk-bound ball of leaflets at the frond tip. An individual larva usually constructs 3 globe shelters on different fronds of the same plant before completing its development. As shelter sites, sterile Polystichum fronds are chosen preferentially over fertile fronds. The bundle and fiddlehead shelter forms, less abundant, appear cryptic to humans and perhaps to other vertebrates. The final globe shelter form is larger and quite conspicuous. However, the persistence of empty globe shelters left on the plant as the larva moves to a new one may serve to make searching for larvae less profitable for potential predators and parasites. We suggest that the energetic costs of constructing and occupying multiple shelters may be offset by circumvention of reduced frond palatability and reduced exposure to predators and parasites.     

Female great tits Parus major do not increase their daily energy expenditure when incubating enlarged clutches

Several studies have shown that enlargement of clutches during incubation reduces the long-term survival of parents. In line with these findings, studies on the energetic costs of nocturnal incubation show an increase in energy expenditure with clutch enlargement. Studies on daily energy expenditure during incubation (DEE_inc), however, do not consistently show such a negative effect of clutch enlargement. To determine whether differential survival results from a direct increase in energy costs or rather from costs associated with compensatory behaviour, we studied the DEE_inc (kJ day⁻¹), change in body mass and nest attendance behaviour of free-living female great tits Parus major that incubated either control or experimentally enlarged clutches. DEE_inc did not differ between the two treatment groups, but was negatively related to mean ambient temperature over the 24-h measuring period, and to the fraction of daytime females spent on the nest. Controlling for these two factors, females incubating enlarged clutches did not spend more energy per 24 h period than females incubating control clutches. Clutch enlargement also did not affect body mass of incubating females, or their nest attendance behaviour. Yet, in the enlarged group body mass change and nest attentiveness were negatively correlated, suggesting that females responded differently to the experimental treatment and thereby preventing us from finding an effect of clutch enlargement.     

Spatial behaviour of sheep during the neonatal period: Preliminary study on the influence of shelter

Effective shelter has been demonstrated to reduce neonatal lamb mortality rates during periods of inclement weather. Periods of high wind speed and rainfall have been shown to influence shelter usage; however, it is not yet known how ewe factors such as breed, age and body condition score influence shelter-seeking behaviour. This study, conducted on a working upland farm in the UK, examined impact of artificial shelter on the biological and climatic factors that influence peri-parturient ewe behaviour. Pregnant ewes (n = 147) were randomly allocated between two adjacent fields which were selected for their similarity in size, topography, pasture management, orientation to the prevailing wind and available natural shelter. In one field, three additional artificial shelters were installed to increase the available shelter for ewes, this field was designated the Test field; no additional artificial shelter was provided in the second field which was used as the Control field. Individual ewes were observed every 2 h between 0800 and 1600 for 14 continuous days to monitor their location relative to shelter. Ewe breed (Aberfield and Highlander), age (2–8 years) and body condition score were considered as explanatory variables to explain flock and individual variance in shelter-seeking behaviour and the prevalence of issues which required the intervention of the shepherd, termed ‘shepherding problems’. Any ewe observed with dystocia, a dead or poor vigour lamb or who exhibited mismothering behaviour was recorded as a shepherding problem. The prevalence of these shepherding problems which necessitate human intervention represents arguably the most critical limiting factor for the successful management of commercial sheep flocks in outdoor lambing systems. Overall, ewes in the Test field with access to additional artificial shelter experienced fewer shepherding problems than those in the Control field (P < 0.05). A significant breed effect was also observed, with Highlander ewes more likely to seek shelter than Aberfield ewes (P < 0.001), and experiencing significantly fewer shepherding interventions (P < 0.05). These findings demonstrate the substantial and significant benefits to animal welfare and productivity that can be achieved through the provision of shelter in commercial, upland, outdoor lambing systems in the UK.     

Behavioural plasticity under a changing climate; how an experimental local climate affects the nest construction of the zebra finch Taeniopygia guttata

Successful reproduction in most avian species is dependent on the construction of a nest that provides protection and a suitable microclimate for the eggs and developing nestlings. Observational studies suggest that climatic variation may affect the structure of the nest, but to date there have been no attempts to experimentally determine the role that local climate plays in the construction of a suitable nest. Using a within‐individual counter balanced design we investigated how nest composition and construction differ in zebra finches breeding in ambient conditions of 18°C and 30°C. We found that at 18°C birds built nests that were over 20% heavier, and with significantly more thread and less grass than those built at 30°C. Our results highlight the degree of plasticity in nest building behaviour in relation to local ambient conditions. These results suggest that nest building behaviour is one route through which birds can respond to a changing climate and modify the microclimate of their nest in line with projected changes in ambient conditions.     

Drought Effects in Climate Change Manipulation Experiments: Quantifying the Influence of Ambient Weather Conditions and Rain-out Shelter Artifacts

Extreme drought events challenge ecosystem functioning. Ecological response to drought is studied worldwide in a growing number of field experiments by rain-out shelters. Yet, few meta-analyses face severe challenges in the comparability of studies. This is partly because build-up of drought stress in rain-out shelters is modified by ambient weather conditions. Rain-out shelters can further create confounding effects (radiation, temperature), which may influence plant responses. Yet, a quantification of ecophysiological effects within rain-out shelters under opposing ambient weather conditions and of microclimatological artifacts is missing. Here, we examined phytometers—standardized potted individuals of Plantago lanceolata—under rain-out shelter, rain-out shelter artifact control, and ambient control during opposing outside microclimatological conditions. Furthermore, we tested for artifacts of rain-out shelters on plant responses in a long-term semi-natural grassland experiment. Phytometer plants below the rain-out shelters showed lower stomatal conductance, maximum quantum efficiency, and leaf water potential during warm ambient conditions with high evaporative demand than during cold conditions with low evaporative demand. Plant performance was highly correlated with ambient temperature and vapor pressure deficit (VPD). Rain-out shelter artifacts on plant responses were nonsignificant. Rain-out shelters remain a viable tool for studying ecosystem responses to drought. However, drought manipulations using rain-out shelters are strongly modified by ambient weather conditions. Attributing the results from rain-out shelter studies to drought effects and comparability among studies and study years therefore requires the quantification of the realized drought stress, for example, by relating ecosystem responses to measured microclimatological parameters such as air temperature and VPD.     

Internal illuminance and shelter shape affect shelter selection by the Japanese eel Anguilla japonica

The present study evaluated the effects of internal illuminance and shelter shape on shelter selection by Japanese eels to enable the preservation or construction of suitable shelters for the Japanese eel. Japanese eels were able to distinguish a 1.25-fold difference in illumination inside the shelters, and preferred darker shelters. When the internal illumination of two shelters with the same shape was less than one-tenth of the ambient illumination (about 400 lx), shelter selection by Japanese eels was not affected by internal illuminance, even when there was a 10-fold difference in internal illumination between shelters. The width of the shelter was not important, but Japanese eels preferred a deep shelter with a low ceiling and walls that spread to a ‘dead end’. This has important implications on the creation of suitable shelters for Japanese eels.     

Indirect interactions mediated by leaf shelters in animal–plant communities

Leaf shelters indirectly mediate interactions in animal–plant communities by providing the occupants with several kinds of benefits, as physical ecosystem engineering. The occupants benefit from favorable microhabitat, reduction in antiherbivore defense, and protection from natural enemies. The primary shelter maker has to spend energy and time and producing silk, but shelter users have great advantages without incurring costs. Shelter users consist of a wide range of arthropod taxa and can be divided into two groups: coexisting organisms that live with a primary shelter maker in the same shelter, and secondary users, which inhabit a leaf shelter after it is utilized by a shelter maker. Leaf shelters mediate interactions between (1) primary shelter makers and coexisting organisms or (2) primary shelter makers and secondary users, (3) secondary users, (4) shelter users and their natural enemies, and (5) primary shelter makers, secondary users, and their host plants. Most interactions between primary shelter makers and coexisting organisms constitute a direct trophic linkage rather than indirect ones. There are actually unidirectional beneficial effects from a primary shelter maker to secondary shelter users, whereas leaf shelters mediate competition and predation among shelter users. By providing a leaf shelter, a shelter maker leads to increased diversity of interactions. Leaf shelters modify the distribution of organisms on the host plant and influence herbivory on the host plant. In tritrophic interactions, leaf shelters act as cues for natural enemies that search for a shelter user as prey. Furthermore, by enhancing habitat heterogeneity, leaf shelters affect the abundance and species richness of arthropods on host plants. Received: July 24, 2000 / Accepted: February 15, 2001     

Reptilian endothermy: a field study of thermoregulation by brooding diamond pythons

Miniature temperature-sensitive radiotransmitters were surgically implanted into free-ranging adult diamond pythons ( Morelia s. spilota ), which are medium-sized boid snakes of south-eastern Australia. Four female pythons oviposited during the study, and constructed incubation mounds. These apparently provided excellent insulation, and the snakes maintained high (approx. 31 C) and relatively constant body temperatures throughout the two-month incubation period. They apparently maintained these temperatures primarily by endogenous heat production (shivering thermogenesis), but also basked briefly on most mornings.
Brooding females maintained a body temperature differential above ambient of about 9C, occasionally up to 13C; their temperatures were significantly higher amd less variable than those of non-brooding females or males. The energetic cost of brooding must be high, but these costs may be outweighed by the benefits of rapid embryonic development and high embryonic survivorship.     

Giant males or dwarf females: what determines the extreme sexual size dimorphism in Lamprologus callipterus?

In the Lake Tanganyika cichlid Lamprologus callipterus , males were >12 times heavier than females, the most extreme sexual size dimorphism in this direction among animals. L. callipterus males construct nests of empty snail shells in which the females breed. If the ancestors of L. callipterus were small cichlids, both sexes may have used shells for shelter. If the ancestors were larger, snail shells could not be used as shelters and would be important only for reproduction. In the field and the laboratory, females bred only in shells and the largest spawned in the largest shells. In the field, females chose larger shells than the average available in males' territories and did not copy the mate choice of other females. They never hid from predators in snail shells and they occurred commonly in areas without any potential shell shelters. In laboratory experiments females used shells only for reproduction and hardly for shelter. Therefore, it seems unlikely that L. callipterus descended from small shell-brooding cichlids which used shells for shelter, but more likely that the ancestors were of large or intermediate size, and that female size is constrained by the sizes of snail shells, which appear to be optimal breeding substrata.     

Reproductive resilience to food shortage in a small heterothermic primate

The massive energetic costs entailed by reproduction in most mammalian females may increase the vulnerability of reproductive success to food shortage. Unexpected events of unfavorable climatic conditions are expected to rise in frequency and intensity as climate changes. The extent to which physiological flexibility allows organisms to maintain reproductive output constant despite energetic bottlenecks has been poorly investigated. In mammals, reproductive resilience is predicted to be maximal during early stages of reproduction, due to the moderate energetic costs of ovulation and gestation relative to lactation. We experimentally tested the consequences of chronic-moderate and short-acute food shortages on the reproductive output of a small seasonally breeding primate, the grey mouse lemur (Microcebus murinus) under thermo-neutral conditions. These two food treatments were respectively designed to simulate the energetic constraints imposed by a lean year (40% caloric restriction over eight months) or by a sudden, severe climatic event occurring shortly before reproduction (80% caloric restriction over a month). Grey mouse lemurs evolved under the harsh, unpredictable climate of the dry forest of Madagascar and should thus display great potential for physiological adjustments to energetic bottlenecks. We assessed the resilience of the early stages of reproduction (mating success, fertility, and gestation) to these contrasted food treatments, and on the later stages (lactation and offspring growth) in response to the chronic food shortage only. Food deprived mouse lemurs managed to maintain constant most reproductive parameters, including oestrus timing, estrogenization level at oestrus, mating success, litter size, and litter mass as well as their overall number of surviving offspring at weaning. However, offspring growth was delayed in food restricted mothers. These results suggest that heterothermic, fattening-prone mammals display important reproductive resilience to energetic bottlenecks. More generally, species living in variable and unpredictable habitats may have evolved a flexible reproductive physiology that helps buffer environmental fluctuations.     

Adaptation to cold and predation—shelter use by invasive raccoon dogs <Emphasis Type="Italic">Nyctereutes procyonoides</Emphasis> in Białowieża Primeval Forest (Poland)

Based on radio-tracking of raccoon dogs Nyctereutes procyonoides in Białowieża Primeval Forest (E Poland) in 1997–2002, we addressed the hypothesis that pattern of shelter use by this invasive carnivore is an adaptation to both climatic conditions and predation. Raccoon dogs used various types of shelters but were invariably concealed in dense vegetation or in the shelters created by trunks, branches, or roots of fallen trees (58% of days). Burrows (mainly badger setts) and hollow trees (mainly fallen limes) were selected on 27% and 14% of days, respectively. The pattern of shelter use varied throughout the year. In crucial periods (breeding period and winter), raccoon dogs used shelter offering better protection: burrows and hollow trees (use of which increased with decreasing ambient temperature) in winter, and hollow trees and dense vegetation during breeding and raising pups. The pattern of shelter use by raccoon dogs was also strongly modified by forest structure. Raccoon dogs living in the pristine old-growth stands (with large amounts of dead wood) utilized mainly natural shelters created by fallen trees (trunks, branches, and roots) and sedge tussocks (38% and 37%, respectively). Individuals inhabiting the managed part of the Forest used mainly burrows (43%) and thicket (23%). We recorded very strong monogamous relationships between pair mates, manifested by shared resting on 84% of days per year. We conclude that hiding behavior and plasticity in shelter use is a response to high mortality due to predation and to unfavorable climatic conditions. High adaptability to various environmental conditions may be one of the factors underlying successful range expansion of raccoon dogs in Europe.     

Effect of weather conditions on the spring migration of Eurasian Woodcock and consequences for breeding

Migration is a critical period of time with fitness consequences for birds. The development of tracking technologies now allows researchers to examine how different aspects of bird migration affect population dynamics. Weather conditions experienced during migration are expected to influence movements and, subsequently, the timing of arrival and the energetic costs involved. We analysed satellite‐tracking data from 68 Eurasian Woodcock Scolopax rusticola fitted with Argos satellite tags in the British Isles and France (2012–17). First, we evaluated the effect of weather conditions (temperature, humidity, wind speed and direction, atmospheric stability and visibility) on migration movements of individuals. Then we investigated the consequences for breeding success (age ratio) and brood precocity (early‐brood ratio) population‐level indices while accounting for climatic variables on the breeding grounds. Air temperature, wind and relative humidity were the main variables related to migration movements, with high temperatures and northward winds greatly increasing the probability of onward flights, whereas a trend towards greater humidity over 4 days decreased the probability of movement. Breeding success was mostly affected by climatic variables on the breeding grounds. The proportion of juveniles in autumn was negatively correlated with temperature in May, but positively correlated with precipitation in June and July. Brood precocity was poorly explained by the covariates used in this study. Our data for the Eurasian Woodcock indicate that, although weather conditions during spring migration affect migration movements, they do not have a major influence on subsequent breeding success.     

Characteristics of African wild dog natal dens selected under different interspecific predation pressures

To successfully reproduce, many carnivorous mammals need access to suitable den sites. Den site selection is often based on fitness related criteria like escape from predators, food availability and shelter from extreme weather conditions. African wild dogs are cooperative breeders that use a den to give birth to their offspring. They often co-exist with lions and spotted hyenas, both of which are known to kill African wild dog pups. Little is known about den site selection by African wild dogs. In this study, we compared vegetation characteristics and distribution of roads and waterholes around den sites and random sites, in areas with high and low lion and spotted hyena densities. In both areas, African wild dogs selected den sites in closed woodland with little visibility, which is likely to reduce detection by predators, increase the likelihood of escape when detected, and might provide shelter from extreme weather conditions. In the high predator density area, African wild dogs seemed to spatially avoid predators by selecting den sites in this type of habitat relatively further away from waterholes and roads. African wild dogs have high energetic costs of gestation. Therefore, even when predation risk is relatively low, they are likely to try to maximise their fitness by choosing a den site in habitat that will provide optimal protection for their offspring, leaving little additional options to respond to a higher predation pressure.     

Combined effect of incubation and ambient temperature on the feeding performance of a small ectotherm

Abstract Many ectothermic animals are subject to fluctuating environmental temperatures during incubation as well as post‐birth. Numerous studies examined the effects of incubation temperature or ambient temperature on various aspects of offspring phenotype. We investigated whether incubation temperature and ambient temperature have an interactive effect on offspring performance. Our study animal, the ectothermic vertebrate Lampropholis delicata (common garden skink; De Vis 1888), experiences fluctuating environmental temperatures caused by differential invasion of an exotic plant Vinca major (blue periwinkle). In the laboratory, eggs from wild‐caught females were assigned to different incubation temperatures that mimicked variation in natural nests. The feeding performance and digestion time of each hatchling was tested at ambient temperatures that represented environments invaded to different degrees by periwinkle. Incubation and ambient temperature interacted to affect a lizard's mobility, the time that it took to capture, subdue and handle a prey, and the number of handling ‘errors’ that it made while foraging. For a number of these characteristics, incubation‐induced changes to a lizard's mass significantly affected this relationship. Irrespective of size, no interaction effect was found for digestion time: lizards digested food faster at warmer temperatures, regardless of incubation temperature. Thus, temperatures experienced during incubation may alter an animal's phenotype so that the surrounding thermal environment differentially affects aspects of feeding performance. Our results also demonstrate that incubation environment can induce changes to morphology and behaviour that carry over into a lizard's early life, and that in some cases these differences in phenotype interact to affect performance. We suggest that the immediate removal of exotic plants as part of a weed control strategy could have important implications for the foraging performance, and presumably fitness, of ectothermic animals.     

Shelters and their use by fishes on fringing coral reefs

Coral reef fish density and species richness are often higher at sites with more structural complexity. This association may be due to greater availability of shelters, but surprisingly little is known about the size and density of shelters and their use by coral reef fishes. We quantified shelter availability and use by fishes for the first time on a Caribbean coral reef by counting all holes and overhangs with a minimum entrance diameter ≥3 cm in 30 quadrats (25 m(2)) on two fringing reefs in Barbados. Shelter size was highly variable, ranging from 42 cm(3) to over 4,000,000 cm(3), with many more small than large shelters. On average, there were 3.8 shelters m(-2), with a median volume of 1,200 cm(3) and a total volume of 52,000 cm(3) m(-2). The number of fish per occupied shelter ranged from 1 to 35 individual fishes belonging to 66 species, with a median of 1. The proportion of shelters occupied and the number of occupants increased strongly with shelter size. Shelter density and total volume increased with substrate complexity, and this relationship varied among reef zones. The density of shelter-using fish was much more strongly predicted by shelter density and median size than by substrate complexity and increased linearly with shelter density, indicating that shelter availability is a limiting resource for some coral reef fishes. The results demonstrate the importance of large shelters for fish density and support the hypothesis that structural complexity is associated with fish abundance, at least in part, due to its association with shelter availability. This information can help identify critical habitat for coral reef fishes, predict the effects of reductions in structural complexity of natural reefs and improve the design of artificial reefs.