Inside Nests Research Articles

House-warming: Wild king cobra nests have thermal regimes that positively affect hatching success and hatchling size

Incubation temperature in nests of oviparous reptiles affects reproductive success indicators, including hatching time and success, offspring size, fitness, and behaviour. The female king cobra builds an above ground nest to incubate and protect its eggs. However, it is not clear how thermal regimes inside king cobra nests respond to external environmental temperature regimes, especially in subtropical regions that witness high diel and seasonal temperature fluctuations. To better understand the relationship between inside nest temperatures and hatching outcomes for this snake, we monitored the thermal regimes of 25 natural king cobra nests in the subtropical forests of the Western Himalayas in Uttarakhand state, northern India. We hypothesized that inside nest temperatures would be higher than outside (ambient) temperatures and that thermal regimes inside nests would affect hatching success and hatchling size. Internal and external temperatures at nest sites were measured every hour until hatching, via automatic data loggers. We then calculated hatching success of eggs and measured hatchling length and weight. Mean inside nest temperatures were consistently higher by about 3.0 °C than outside environmental temperatures. External temperature reduced with increasing elevation of nest sites and was the best determinant of inside nest temperature, which had a smaller range of variability. Physical characteristics of nests (size and leaf materials used) did not influence nest temperature significantly, but nest size was positively related to clutch size. Mean inside nest temperature was the best predictor of hatching success. Average daily minimum nest temperature, which indicates a possible lower threshold for thermal tolerance by eggs, was also correlated positively with hatching success. Mean daily maximum temperature was a significant predictor of mean length of hatchlings, but not of mean hatchling weight. Our study provides unequivocal evidence for the critical thermal benefits of king cobra nests for increased reproductive success, in subtropical environments with lower and sharply fluctuating temperature regimes.

Experimental manipulation of cavity temperature produces differential effects on parasite abundances in blue tit nests at two different latitudes.

Although different predictive models forecast that climate change will alter the distribution and incidence of parasitic diseases, few studies have investigated how microclimatic changes may affect host-parasite relationships. In this study, we experimentally increased the temperature inside nest boxes of the blue tit Cyanistes caeruleus during the nestling period at two different latitudes (central Spain and central Germany) to determine its effect on parasite abundance. The two localities have contrasting climate conditions: the southern one in Spain is warmer and drier than the northern one in Germany. Consistent with this, we observed that the parasitic fauna in nests at the two localities differs. The flea species Ceratophyllus gallinae was more abundant in the northern locality, while the blowfly species Protocalliphora azurea and biting midge species of the genus Culicoides were more abundant in the southern one, as were blood parasites. Moreover, dermanyssid mites and blackflies (Simuliidae) were observed only in the southern locality. The temperature inside nest boxes was increased using heat mats placed underneath the nest material during the nestling period (day 3 to day13 post-hatching). Compared with control nests, the average temperature in heated nests increased by 2.24 °C and 1.35 °C at night in Spain and Germany, respectively. Consequently, the average relative humidity in heated versus control nests decreased 4.93 and 0.82 units in Spain and Germany, respectively. The abundance of blowfly pupae in the heated nests was significantly lower than that of control nests at both localities. The abundance of larval fleas was also lower in the heated nests, but only at the Spanish locality. Infection by the blood parasites Haemoproteus/Plasmodium was higher in males attending the heated nests in Germany, and the control nests in Spain. Moreover, both male body mass and nestling wing length were negatively related to the abundance of larval fleas. In conclusion, our results indicate that increased temperature at the nestling stage may affect the fitness of blue tits by altering parasite prevalence rates.

Influence of the Number of Queens on Nest Establishment: Native and Invasive Ant Species.

Simple SummaryNest establishment is a critical stage of the ant life cycle because it determines the chances of colony success. Here, we study the effect of different numbers of queens (i.e., one or six) on the position of queens and workers inside and outside the artificial nests of an invasive (Linepithema humile) and Mediterranean native (Tapinoma nigerrimum) species. Our results suggest that queens in nests with six queens entered the nest faster than single queens. Similarly, during nest establishment, workers in nests with six queens entered the nest faster, with this effect being more pronounced for the native species. Once nests were established, fewer workers were engaged in outside-nest tasks in nests with six queens. This was especially true for workers of the native species engaged in patrolling. These results suggest that the number of queens can influence both queen and worker behavior, and that invasive and native species have different responses.As a critical stage in the life cycle of ant colonies, nest establishment depends on external and internal factors. This study investigates the effect of the number of queens on queen and worker behavior during nest establishment in invasive Argentine ants (Linepitema humile) and native Mediterranean Tapinoma nigerrimum. We set up experimental colonies with the same number of workers but with one or six queens. At different time points, we recorded the positions of queens and workers inside and outside the nest. Our results highlight the influence of the number of queens on the position of queens and workers with between-species differences. Queens of both species entered the nests more quickly when there were six queens. During nest establishment, more workers were inside nests with six queens for both species, with this effect being greater for T. nigerrimum. Once nests were established, fewer workers of both species were engaged in nest maintenance and feeding in nests with six queens; T. nigerrimum had fewer workers engaged in patrolling. These results suggest that the number of queens is a key factor driving queen and worker behavior during and after nest establishment with different species responses.

The specialized thoracic skeletomuscular system of the myrmecophile Claviger testaceus (Pselaphinae, Staphylinidae, Coleoptera)

External and internal structures of the thorax of the myrmecophile beetle Claviger testaceus (Clavigeritae, Pselaphinae) were examined and documented with state-of-the-art visualization techniques. Following a general trend in the omaliine lineage (Staphylinidae), the skeletal elements of the pro- and pterothorax in Claviger reach a maximum degree of compactness, with largely reduced inter- and intrasegmental sutures and skeletal elements linked with the flight apparatus. The musculature, especially metathoracic direct and indirect flight muscles, also shows a high degree of reduction. Two forms of wings were found among individuals of C. testaceus, both non-functional and representing an advanced stage of reduction. However, that wing vestiges are still present and the metanotum, only slightly reduced, suggests that loss of flight in this species is likely the result of a young evolutionary process. Several structures are linked with myrmecophilous habits: small body size facilitates transportation of beetles by ant workers and makes it easier to move inside nest tunnels; the remarkably compact body and mechanically robust appendages make the beetles less vulnerable to attacks by ant mandibles; the improved elytral interlocking mechanism and unusually expanded epipleura enhance the protection of vulnerable dorsal parts of the pterothorax and anterior abdomen; and glands associated with trichomes on the posterolateral elytral angle produce secretions attractive for ants. Various modifications of the thorax and anterior abdomen lead to an optimization of intimate associations with ants. The morphological syndrome enabling these beetles to cope with life in ant colonies evolved in several steps. This is suggested by an increasing solidification of the thoracic skeleton in related non-myrmecophilous groups and also by less modified related clavigerites;for instance, ant-associated tropical species are still able to fly.

A report of unusual aggregation behaviour in Bullsnakes (<i>Pituophis catenifer sayi</i>) near a nest site in Saskatchewan

We describe an unusual aggregation of Bullsnakes (Pituophis catenifer sayi) near a nest site in Saskatchewan. Bullsnake is a wide-ranging oviparous colubrid that reaches the northern tip of its continental range on the prairies and badlands of Canada. At that location, it is considered a species of Special Concern, but, until recently, has been the subject of relatively few natural history reports. This is significant, because, at the northern edge of their range, Bullsnakes may behave differently than elsewhere due to thermal limitations experienced at high latitudes. On 29 June 2019, we observed a mass of five adult Bullsnakes in a Silver Sagebrush (Artemisia cana) shrub on a slope in southwestern Saskatchewan. Aggregations of Bullsnakes are known to occur at hibernacula, during mating, and inside nest chambers before and after oviposition. However, we are unaware of the occurrence of surface aggregations in any other situation. We suggest that these Bullsnakes may have been exhibiting communal gestation, a behaviour thought to be rare in oviparous snakes whereby gravid females congregate before parturition or oviposition for thermal stability or protection from predators.

Nest Gasses as a Potential Attraction Cue for Biting Flying Insects and Other Ectoparasites of Cavity Nesting Birds

The presence of nestlings and other nest dwelling living beings in nests built in cavities alter the composition of gases inside the cavity. This different concentration of gases could be used by some parasites as a cue to localize their hosts. Here, we explored the temporal variation in the concentration and isotopic signature of carbon dioxide (CO2) and methane (CH4) inside nest boxes of blue tits Cyanistes caeruleus during the nestling period (days 3, 8, 13, 20 and 21 post-hatching) as well as several variables potentially affecting such variation. Finally, we checked whether difference in gases concentration affects the number of different types of parasites affecting nestlings. Concentration of gases and isotopic signature were significantly different between nest cavities and the forest during the nestling period. CO2 concentration was higher while CH4 was lower inside nests than in forest air. We expect that the abundance of those parasites seeking actively for nests (blackflies, biting midges and blowflies) could be related with differences in gases concentrations if they use these differences as a cue for host location. In this respect, abundance of biting midges were related positively with differences in CO2 between nest and forest at day 20 of nestling age indicating that these mosquitoes can use concentrations of that gas to find their host. In addition, we found a positive relationship between blackflies and differences in CH4 concentration. However, concentration of this gas inside nests may be related with bacterial activity and therefore this relationship may be due to an effect of bacteria on blackflies and not to the effect of gas as a blackfly attractant to nests. Other relationships between difference on gases concentration and mites were found but due to the way these parasites use to reach nests (i.e.: transported by adult birds) we discard the possibility that they use that difference as a cue for host location. Brood size was also related with mite and flea abundances and relative humidity with flea abundance. In addition, the condition of blue tit females was negative and significantly related with the abundance of blowfly pupae.

Predator scent and visual cue applied to nest boxes fail to dissuade European Starlings (Sturnus vulgaris) from nesting

Indirect predator cues have been shown to enhance perceived nest predation risk in both open-cup and cavity-nesting birds. We hypothesized that scent from the raccoon (Procyon lotor) inside nest boxes, supplemented with raccoon hair as a visual cue on the outside of the box, would enhance perceived risk to the European Starling (Sturnus vulgaris), resulting in reduced use of treated nest boxes and negative effects on reproduction. The starling is recognized, outside its native range, as a competitor with indigenous cavity nesters and a pest species, and efforts to deter its nesting have generally been unsuccessful. Our objectives were to examine nest initiation, clutch development, and hatching success by starlings relative to 4 nest box treatments. Starlings selected from nest boxes treated with a novel visual cue at the entry hole, predator scent inside the nest box and supplemented with a predator visual cue at the entry hole, the predator visual cue, or a novel odor inside the box and supplemented with the novel visual cue at the entry hole (n = 120 boxes; n = 30 per treatment). Starlings established nest bowls in 65% of nest boxes (novel visual cue = 21 boxes, predator scent/predator visual cue = 19 boxes, predator visual cue = 17 boxes, novel odor/novel visual cue = 21 boxes); clutches (≥1 egg) were laid in 80 boxes, but 2 boxes contained a single egg with no nest. We observed no effects of treatment on likelihood of starlings laying a clutch, date of first egg, clutch size, or hatchling number. We conclude that raccoon scent inside nest boxes, supplemented by raccoon hair as a visual cue, failed to enhance perceived risk to starlings such that nesting was deterred. We suggest that direct or indirect experience with nest predation attempts (which enhance perceived risk) and the starling's plasticity in antipredator responses are key hurdles in development of an efficacious nesting deterrent. Therefore, we encourage the evaluation of direct predation risk via use of predator effigies on or in nest boxes, as well as in foraging areas proximate to nest boxes.

Early-life exposure to artificial light at night elevates physiological stress in free-living songbirds☆

Artificial light at night (ALAN) can disrupt adaptive patterns of physiology and behavior that promote high fitness, resulting in physiological stress and elevation of steroid glucocorticoids (corticosterone, CORT in birds). Elevated CORT may have particularly profound effects early in life, with the potential for enduring effects that persist into adulthood. Research on the consequences of early-life exposure to ALAN remains limited, especially outside of the laboratory, and whether light exposure affects CORT concentrations in wild nestling birds particularly remains to be elucidated. We used an experimental setup to test the hypothesis that ALAN elevates CORT concentrations in developing free-living birds, by exposing nestling great tits (Parus major) to ALAN inside nest boxes. We measured CORT in feathers grown over the timeframe of the experiment (7 nights), such that CORT concentrations represent an integrative metric of hormone release over the period of nocturnal light exposure, and of development. We also assessed the relationships between feather CORT concentrations, body condition, nestling size rank and fledging success. In addition, we evaluated the relationship between feather CORT concentrations and telomere length. Nestlings exposed to ALAN had higher feather CORT concentrations than control nestlings, and nestlings in poorer body condition and smaller brood members also had higher CORT. On the other hand, telomere length, fledging success, and recruitment rate were not significantly associated with light exposure or feather CORT concentrations. Results indicate that exposure to ALAN elevates CORT concentrations in nestlings, which may reflect physiological stress. In addition, the organizational effects of CORT are known to be substantial. Thus, despite the lack of an effect on telomere length and survivorship, elevated CORT concentrations in nestlings exposed to ALAN may have subsequent impacts on later-life fitness and stress sensitivity.

A female perspective: testing the effects of noise masking on signal transmission patterns inside the nest box

Abstract During the breeding season, avian pairs coordinate interactions with songs and calls. For cavity nesting birds, females inside nest boxes may rely on male vocalizations for information. Anthropogenic noise masks male songs, which could affect information gained by females. We explored song transmission from a female house wren (Troglodytes aedon) perspective, testing the hypothesis that noise masking alters songs that reach females inside nest boxes. We broadcast songs at three distances up to 25 m from nest boxes and re-recorded songs using two microphones, positioned inside and outside nest boxes. We measured signal-to-noise ratios and cross-correlation factors to estimate the effects of masking on transmission. In noise, songs received inside nest boxes had lower signal-to-noise ratios and cross-correlation factors than songs recorded outside of boxes, and these effects decreased with distance. For females, noise may reduce information conveyed through male songs and in response pairs may need to adjust their interactions.

Diurnal patterns of ambient temperature but not precipitation influence incubation behavior in Great Tits

Environmental conditions affect incubation behavior, but whilst the effect of ambient temperature is studied and still controversially discussed, the role of precipitation is unknown. Here, we analyzed the effect of local ambient temperature and precipitation on incubation behavior of female Great Tits (Parus major) and accounted for diurnal patterns of weather conditions. We monitored the incubation behavior of females using temperature data loggers, thus identifying periods of staying inside nest boxes incubating, and leaving nest boxes (off-bout). In total, 685 single off-bouts were analyzed between the first 8 days of incubation directly after clutches were completed. Our study showed that whilst precipitation had no effect on incubation behavior, number and duration of off-bouts were negatively related to ambient temperature, which varied throughout the day. We showed that females took longer off-bouts during low-temperature early mornings, which may result from the need to forage after fasting during the night. Thus, foraging in the early morning seemed to outcompete energy requirements during these cold temperature periods. In addition, females spent less time off the nest as incubation progressed. Our results emphasize that patterns of incubation behavior cannot be understood without taking into account varying temperature conditions throughout the day.

Light affects parental provisioning behaviour in a cavity‐nesting Passerine

Nocturnal bird species possess special adaptations to maximise visual efficiency under low light levels. However, some typically diurnal species also experience low‐light environments. For example, cavity‐nesting Passerines raise broods in dark cavities and search for food in light‐abundant surroundings. It is not clear whether they possess special adaptations for low light vision or breed in cavities at the expense of impaired parental care. In this study, we tested whether light conditions affect the provisioning efficiency of great tits. We experimentally tested how the level of natural and artificially increased illumination inside nest boxes affects parental feeding duration, frequency and timing. We monitored 15‐h of provisioning activity of great tit parents when nestlings were day seven post hatch. We used traditional ‘dark’ nest boxes and ‘bright’ nest boxes with increased illumination obtained by using semi‐transparent plastic windows. The duration of single feedings were, on average, shorter in brightened nest boxes compared to dark ones. This difference tended to be higher early in the morning and in the evening, when the illumination in dark nest boxes was the lowest. Nest box type, however, did not influence feeding frequency or times of the onset and the end of feeding. Our findings provide new evidence for impaired efficiency of parental care due to lowered light conditions. Further research is needed to test whether prolonged feeding duration has negative effects on adult time budgets and nestling energy expenditures.

Behavioural analysis of Village Weavers Ploceus cucullatus in an Ethiopian breeding colony during incubation: 1. Females

We used video recordings to perform a behavioural analysis of a Village Weaver Ploceus cucullatus colony in Awash National Park, Ethiopia. We focused specifically on female behaviour during the pair-formation, egg-laying and early-incubation phases of the nesting cycle. A factor analysis revealed that females’ temporal investments can be partitioned into three broad behavioural categories: (1) behaviours associated with aggression, (2) time away/ inside nest, and (3) behaviours associated with copulation. Time budgets revealed females spent approximately 61% of their time away from the colony and 38% of their time inside their nests. The performance of individual behaviours was largely a function of temporal and social factors, including when the birds were observed and the personality of the territorial male. Females invested more time away from the nest earlier and more time inside the nest later in the observation period. One aspect of a territorial male’s personality, boldness, was a predictor of several female behaviours: a female Village Weaver was significantly more likely to remain on a territory if the resident male had a tendency not to flee during colony-wide disturbances. Lastly, a path analysis revealed that females exhibited consistent sequential patterns of behaviour.

Rhopalomastix is only the second ant genus known to live with armoured scale insects (Diaspididae)

Rhopalomastix is a myrmicine ant distributed throughout tropical parts of Asia, with almost nothing known about its biology. Its closest relative Melissotarsus in Africa is the only ant genus known to live with diaspidid scale insects inside their nests, and to rely on these for food. Twelve colonies of four species of Rhopalomastix were sampled from seven tree genera in Singapore. Ants chewed tunnels under live bark, and these were occupied by many diaspidids belonging to five genera; at least two species are known to also live freely on the outside of trees. Inside ant nests, only a few diaspidids secreted their trademark shields. The association with the pupillarial Fiorinia is unexpected, since they have fewer secretions that can be used as food by the ants. Rhopalomastix and Melissotarsus workers share several morphological adaptations, including powerful mandibles and silk glands, but while the legs of Melissotarsus are modified for traction during tunnelling, those of Rhopalomastix are not. Consequently, Rhopalomastix workers are able to walk outside their tunnels, but they behaved timidly except in R. murphyi. Silk was used to repair damaged tunnels, and the spinning behaviour resembled that of Melissotarsus. Host trees do not gain protection from the ants against leaf herbivores, so they apparently get no benefits from this mutualism. We discuss the likely economic impact of this parasitic lifestyle, especially on fruit trees.

A new genus of armoured scale insect for a new scale-less species living inside nests of the ant Rhopalomastix johorensis in Singapore (Hemiptera, Coccomorpha, Diaspididae)

A new genus of armoured scale insect for a new scale-less species living inside nests of the ant Rhopalomastix johorensis in Singapore (Hemiptera, Coccomorpha, Diaspididae)

Auditory neural networks involved in attention modulation prefer biologically significant sounds and exhibit sexual dimorphism in anurans.

Allocating attention to biologically relevant stimuli in a complex environment is critically important for survival and reproductive success. In humans, attention modulation is regulated by the frontal cortex, and is often reflected by changes in specific components of the event-related potential (ERP). Although brain networks for attention modulation have been widely studied in primates and avian species, little is known about attention modulation in amphibians. The present study aimed to investigate the attention modulation networks in an anuran species, the Emei music frog (Babina daunchina). Male music frogs produce advertisement calls from within underground nest burrows that modify the acoustic features of the calls, and both males and females prefer calls produced from inside burrows. We broadcast call stimuli to male and female music frogs while simultaneously recording electroencephalographic (EEG) signals from the telencephalon and mesencephalon. Granger causal connectivity analysis was used to elucidate functional brain networks within the time window of ERP components. The results show that calls produced from inside nests which are highly sexually attractive result in the strongest brain connections; both ascending and descending connections involving the left telencephalon were stronger in males while those in females were stronger with the right telencephalon. Our findings indicate that the frog brain allocates neural attention resources to highly attractive sounds within the window of early components of ERP, and that such processing is sexually dimorphic, presumably reflecting the different reproductive strategies of males and females.

Foraging traits modulate stingless bee community disassembly under forest loss.

Anthropogenic land use change is an important driver of impacts to biological communities and the ecosystem services they provide. Pollination is one ecosystem service that may be threatened by community disassembly. Relatively little is known about changes in bee community composition in the tropics, where pollination limitation is most severe and land use change is rapid. Understanding how anthropogenic changes alter community composition and functioning has been hampered by high variability in responses of individual species. Trait-based approaches, however, are emerging as a potential method for understanding responses of ecologically similar species to global change. We studied how communities of tropical, eusocial stingless bees (Apidae: Meliponini) disassemble when forest is lost. These bees are vital tropical pollinators that exhibit high trait diversity, but are under considerable threat from human activities. We compared functional traits of stingless bee species found in pastures surrounded by differing amounts of forest in an extensively deforested landscape in southern Costa Rica. Our results suggest that foraging traits modulate competitive interactions that underlie community disassembly patterns. In contrast to both theoretical predictions and temperate bee communities, we found that stingless bee species with the widest diet breadths were less likely to persist in sites with less forest. These wide-diet-breadth species also tend to be solitary foragers, and are competitively subordinate to group-foraging stingless bee species. Thus, displacement by dominant, group-foraging species may make subordinate species more dependent on the larger or more diversified resource pool that natural habitats offer. We also found that traits that may reduce reliance on trees-nesting in the ground or inside nests of other species-correlated with persistence in highly deforested landscapes. The functional trait perspective we employed enabled capturing community processes in analyses and suggests that land use change may disassemble bee communities via different mechanisms in temperate and tropical areas. Our results further suggest that community processes, such as competition, can be important regulators of community disassembly under land use change. A better understanding of community disassembly processes is critical for conserving and restoring pollinator communities and the ecosystem services and functions they provide.

Data integration from pathology slides for quantitative imaging of multiple cell types within the tumor immune cell infiltrate

BackgroundImmune cell infiltrates (ICI) of tumors are scored by pathologists around tumor glands. To obtain a better understanding of the immune infiltrate, individual immune cell types, their activation states and location relative to tumor cells need to be determined. This process requires precise identification of the tumor area and enumeration of immune cell subtypes separately in the stroma and inside tumor nests. Such measurements can be accomplished by a multiplex format using immunohistochemistry (IHC).MethodWe developed a pipeline that combines immunohistochemistry (IHC) and digital image analysis. One slide was stained with pan-cytokeratin and CD45 and the other slide with CD8, CD4 and CD68. The tumor mask generated through pan-cytokeratin staining was transferred from one slide to the other using affine image co-registration. Bland-Altman plots and Pearson correlation were used to investigate differences between densities and counts of immune cell underneath the transferred versus manually annotated tumor masks. One-way ANOVA was used to compare the mask transfer error for tissues with solid and glandular tumor architecture.ResultsThe overlap between manual and transferred tumor masks ranged from 20%–90% across all cases. The error of transferring the mask was 2- to 4-fold greater in tumor regions with glandular compared to solid growth pattern (p < 10−6). Analyzing data from a single slide, the Pearson correlation coefficients of cell type densities outside and inside tumor regions were highest for CD4 + T-cells (r = 0.8), CD8 + T-cells (r = 0.68) or CD68+ macrophages (r = 0.79). The correlation coefficient for CD45+ T- and B-cells was only 0.45. The transfer of the mask generated an error in the measurement of intra- and extra- tumoral CD68+, CD8+ or CD4+ counts (p < 10−10).ConclusionsIn summary, we developed a general method to integrate data from IHC stained slides into a single dataset. Because of the transfer error between slides, we recommend applying the antibody for demarcation of the tumor on the same slide as the ICI antibodies.

Does nest box use reduce the fitness of a tree‐cavity dependent mammal?

AbstractNest boxes are frequently used in conservation programs for tree‐cavity dependent wildlife. There is growing concern that the poor insulation properties of nest boxes may produce an ecological trap, because species may require microclimates less extreme or less variable than those experienced inside nest boxes. I investigated the fitness consequences of nest box use in a non‐flying mammal. Fifty‐two of 104 squirrel gliders (Petaurus norfolcensis) trapped over a 3‐year period used nest boxes. Population modelling of the capture data revealed that the probability of apparent survival increased with increasing nest box use. There was no difference in breeding frequency between females that used or did not use nest boxes. There was no evidence that offspring development was hindered within nest boxes. These findings may arise because: (1) gliders could access tree hollows during extreme temperatures, (2) ambient temperatures were mild during the study, (3) gliders construct leaf nests which insulate against low temperatures in winter, and (4) gliders breed between autumn and spring when temperatures are relatively benign. The estimate of annual survival of animals using nest boxes (0.60), was equivalent to estimates at locations where squirrel gliders were either reliant on nest boxes (0.54) or on tree cavities (0.55) for shelter. Studies such as this need to be conducted on a range of species across a range of locations to better understand the influence of nest box use on non‐flying mammals.

Role of chemical and visual cues of mammalian predators in nest defense in birds

We explore for the first time the relative importance of chemical and visual cues of predators in nest defense and antipredator behavior in a hole-nesting songbird, the blue tit Cyanistes caeruleus. Birds breeding in nest boxes were exposed to chemical or visual cues of a predatory and a non-predatory mammal during the nestling stage, and their behavior both outside and inside nest boxes was recorded with video films. Our results show that birds respond equally to chemical and to visual cues of predators in a context of nest defense. Adult birds minimized predation risk by decreasing the time spent inside the nest box while feeding nestlings when they were exposed to either visual or chemical cues of a mammalian predator. They decreased the time spent in non-essential activities for nestlings’ survival, such as nest sanitation activities, but they maintained provisioning rates so that the nestlings’ growth was not compromised. In this way, birds minimized the risk of predation while provisioning nestlings when a predator was detected in the vicinity of their nest. We explored the role of predator chemical and visual cues for risk assessment in blue tits. Our results showed for the first time that birds respond equally to chemical and to visual cues of mammalian predators. Birds decreased time exposed to predation risk when entering the nest box to feed the nestlings. They reduced time spent in non-essential activities for nestling survival, such as nest sanitation. However, they maintained provisioning rates so that nestling growth was not impaired.

Limits to sustained energy intake XXIV: impact of suckling behaviour on the body temperatures of lactating female mice.

The objective of this study was to investigate the potential causes of high body temperature (Tb) during lactation in mice as a putative limit on energy intake. In particular we explored whether or not offspring contributed to heat retention in mothers while suckling. Tb and physical activity were monitored in 26 female MF1 mice using intraperitoneally implanted transmitters. In addition, maternal behaviour was scored each minute for 8 h d−1 throughout lactation. Mothers that raised larger litters tended to have higher Tb while nursing inside nests (P < 0.05), suggesting that nursing offspring may have influenced heat retention. However, Tb during nursing was not higher than that recorded during other behaviours. In addition, the highest Tb during the observation period was not measured during nursing behaviour. Finally, there was no indication that mothers discontinued suckling because of a progressive rise in their Tb while suckling. Tb throughout lactation was correlated with daily increases in energy intake. Chronic hyperthermia during lactation was not caused by increased heat retention due to surrounding offspring. Other factors, like metabolic heat produced as a by-product of milk production or energy intake may be more important factors. Heat dissipation limits are probably not a phenomenon restricted to lactation.