Wood mice aggressiveness and flight response to human handling: Effect of individual and environmental factors

Numerous studies have examined human disturbance repercussions on wildlife, mainly focused on the effects on behaviour, reproductive success and population dynamics. However, few studies have addressed the behaviour of prey species during and after human capture and handling and how this may correlate to individual characteristics or variation in their physical environment they inhabit. We explored wood mouse’s fleeing and aggressive behaviours in response to captures by human in their natural habitat. Eighty‐seven wood mice were caught using Sherman live traps. For each trapped individual, aggressiveness was measured as the total number of bites inflicted upon the investigator during handling time. Afterwards, each mouse was released in a two‐metre radius partially covered vegetation area that allowed visual mouse tracking by the observer and flight behaviour was registered by individual one‐zero focal sampling technique during 2 min. Both aggressiveness and fleeing behaviour were analysed regarding individual (sex, reproductive status, age) and environmental factors (habitat and season). Males, adults and breeding individuals showed heightened aggression levels. Higher aggressiveness levels were found in wood mice occupying scrubland and during summer and autumn. The flight response was exclusively explained by reproductive status, whereby breeding individuals spent more time on fast escape than nonbreeding ones. These results indicate that both individual and environmental factors seem to influence defensive behaviours in the wood mouse during and after being captured by a human. Since human disturbance shares many aspects with the predation risk, behavioural responses found to captures may likely be influenced by previous experience of individuals with predators as well as to seasonal and habitat features conditioning predators’ densities but also protection against them.     

Effects of investigator disturbance on corticosterone concentrations of Black‐legged Kittiwake chicks

ABSTRACT Recent studies indicate that young seabird chicks exposed to relatively short periods of elevated levels of plasma corticosterone may suffer lifelong cognitive impairment that is detrimental to their survivorship and fitness as adults. We examined the chronic effects of investigator disturbance on the baseline and acute stress‐induced levels of plasma corticosterone of Black‐legged Kittiwake (Rissa tridactyla) chicks in Chiniak Bay, Kodiak Island, Alaska, in 2005. Kittiwake chicks were assigned to one of three disturbance treatments: (1) routine handling, (2) exposure to investigator presence, but not handled, and (3) neither handled nor exposed to investigator presence prior to sampling. At 12–15 d posthatching, blood samples were collected to determine baseline and stress‐induced concentrations of corticosterone. We found no significant differences in baseline or stress‐induced levels of corticosterone among the three disturbance treatments. Our results suggest that Black‐legged Kittiwake chicks do not perceive investigator presence as a stressor. However, investigators studying kittiwakes at other locations should proceed with caution because sampling protocols and environmental conditions may differ, potentially causing chicks to perceive disturbances differently as well.     

Absence from the nest due to human disturbance induces higher nest predation risk than natural recesses in Common Eiders Somateria mollissima

Human disturbance of nesting birds may cause reduced breeding success. It is therefore necessary to assess the impact of disturbance to identify steps that minimize negative impacts. We carried out a study of nesting success at two adjacent colonies of Common Eider Somateria mollissima on the islands of Grindøya and Håkøya in northern Norway between 2006 and 2011. Over the study period, nesting success was consistently higher on Håkøya (69–82%) than on Grindøya (35–60%). Between 2009 and 2011 we used camera monitoring of individual nests to identify determinants of nest survival and predation, focusing in particular on the effect of departures from the nest due to human disturbance, which differed between the colonies due to a long‐term research project on Grindøya. Overall, absence of Common Eiders from nests due to disturbance increased the predation risk by a factor of 6.42 for an increase of one additional daily disturbance. In contrast, absence due to natural recesses did not increase nest losses. Under high levels of human disturbance, camera monitoring indicated that the main cause of breeding failure was predation, primarily by Hooded Crows Corvus cornix, but also to some extent Great Black‐backed Gulls Larus marinus. The presence of cameras did not increase the predation risk. Both the presence of researchers and the sight of Common Eider females conspicuously departing from nests are likely to have provided cues to these predators. We suggest management trials to reduce nesting disturbance through the guarding of unoccupied nests to mitigate the effects of human disturbance on reproductive success.     

Radio‐transmitters do not affect seasonal productivity of female Golden‐winged Warblers

Investigating the potential effects of handling and marking techniques on study animals is important for correct interpretation of research results and to effect progress in data‐collection methods. Few investigators have compared the reproductive output of radio‐tagged and non‐radio‐tagged songbirds, and no one to date has examined the possible effect of radio‐tagging adult songbirds on the survival of their fledglings. In 2011 and 2012, we compared several parameters of reproductive output of two groups of female Golden‐winged Warblers (Vermivora chrysoptera) breeding in Minnesota, including 45 females with radio‐transmitters and 73 females we did not capture, handle, or mark. We found no difference between groups in clutch sizes, hatching success, brood sizes, length of incubation and nestling stages, fledging success, number of fledglings, or survival of fledglings to independence. Thus, radio‐tags had no measurable impact on the productivity of female Golden‐winged Warblers. Our results build upon previous studies where investigators have reported no effects of radio‐tagging on the breeding parameters of songbirds by also demonstrating no effect of radio‐tagging through the post‐fledging period and, therefore, the entire breeding season.     

Assessing the effects of repeated handling on the physiology and condition of semi‐precocial nestlings

Repeated exposure to elevated levels of glucocorticoids during development can have long‐term detrimental effects on survival and fitness, potentially associated with increased telomere attrition. Nestling birds are regularly handled for ecological research, yet few authors have considered the potential for handling‐induced stress to influence hormonally mediated phenotypic development or bias interpretations of subsequent focal measurements. We experimentally manipulated the handling experience of the semi‐precocial nestlings of European Storm Petrel Hydrobates pelagicus to simulate handling in a typical field study and examined cumulative effects on physiology and condition in late postnatal development. Neither baseline corticosterone (the primary glucocorticoid in birds), telomere length nor body condition varied with the number of handling episodes. The absence of a response could be explained if Storm Petrels did not perceive handling to be stressful or if there is dissociation of the hypothalamic–pituitary–adrenal axis from stressful stimuli in early life. Eliciting a response to a stressor may be maladaptive for cavity‐dwelling young that are unable to escape or defend themselves. Furthermore, avoiding elevated overall glucocorticoid exposure may be particularly important in a long‐lived species, in which accelerated early‐life telomere erosion could impact negatively upon longevity. We propose that the level of colony‐wide disturbance induced by investigator handling of young could be important in underlining species‐specific responses. Storm Petrel nestlings appear unresponsive to investigator handling within the limits of handling in a typical field study and handling at this level should not bias physiological and morphological measurements.     

Investigator disturbance reduces reproductive success in Short‐tailed Shearwaters Puffinus tenuirostris

Research procedures can have a detrimental effect on the reproductive success of the study species. In this study, the frequency of investigator disturbance on Short‐tailed Shearwaters Puffinus tenuirostris was examined experimentally throughout the incubation period to assess whether disturbance influences hatching success, pre‐fledging chick survival and chick body size. Handling of incubating birds every day, every 3 days and once a week reduced hatching success by 100, 61 and 39%, respectively, compared with pairs that were not disturbed. Most failures resulted from egg abandonment by the parents, particularly during the early stage of incubation. Chick survival did not differ between treatment groups, but control chicks were significantly heavier and had larger bill depths and longer wings. The difference in chick body mass and size observed between the control and disturbed chicks might be due to physiological or behavioural mechanisms in adults or carry‐over effects from the incubation stage to the next life‐history stage. Reduced offspring quality has the potential to affect post‐fledging survival and recruitment. These findings are significant in broader terms because any investigator disturbance that reduces reproductive success, survival and offspring fitness could interfere with the accurate assessment of demographic parameters and exacerbate population declines.     

Winter territoriality and its implications for the breeding ecology of White-throated Dippers Cinclus cinclus

Capsule: Pairs of White-throated Dippers Cinclus cinclus which defended winter territories bred earlier than non-territorial individuals, but there was no difference in reproductive success.

Aims: The effect of winter territoriality on breeding ecology has rarely been studied in resident birds. We carried out a preliminary investigation of whether winter territorial behaviour and territory size affect the timing of reproduction, breeding territory size and reproductive success in a riverine bird, the White-throated Dipper.

Methods: We monitored an individually marked population of White-throated Dippers in the UK. Wintering individuals were classified as either territorial or ‘floaters’ according to their patterns of occurrence and behaviour, and their nesting attempts were closely monitored in the subsequent months. Winter and breeding territory sizes were measured by gently ‘pushing’ birds along the river and recording the point at which they turned back.

Results: All birds defending winter territories did so in pairs, but some individuals changed partners before breeding. Territorial pairs that were together throughout the study laid eggs significantly earlier than pairs containing floaters and those comprising territorial birds that changed partners. However, there were no significant differences in clutch size, nestling mass or the number of chicks fledged. There was no relationship between winter territory length and lay date or any measure of reproductive success, although sample sizes were small. Winter territories were found to be significantly shorter than breeding territories.

Conclusion: Winter territoriality may be advantageous because breeding earlier increases the likelihood that pairs will raise a second brood, but further study is needed. Territories are shorter in winter as altitudinal migrants from upland streams increase population density on rivers, but this may also reflect seasonal changes in nutritional and energetic demands.     

Trapping initiates stress response in breeding and non-breeding house sparrows Passer domesticus: implications for using unmonitored traps in field studies

In response to a variety of unpredictable conditions, birds secrete the steroid hormone corticosterone, which has numerous effects on physiology and behavior. A standardized protocol of handling and restraint has been demonstrated to elicit a robust corticosterone response in many species of birds. In contrast, comparatively little is known about the effects of capture technique on corticosterone secretion in wild birds. Setting up multiple live traps checked at regular intervals allows field researchers to capture many birds in a short period of time. However, one potential drawback of this technique is that birds may spend unknown lengths of time in traps prior to sampling. Many birds appear to remain calm and/or feed during this period, potentially leading researchers to assume that corticosterone secretion is unaffected by trapping. We assessed the impact of being left in traps for up to 30 minutes on baseline corticosterone and subsequent corticosterone responses to restraint in non‐breeding and breeding house sparrows Passer domesticus. Traps were baited with seed, and birds were either removed immediately after entry (controls), or left in the trap undisturbed for 15 or 30 min. Upon removal, birds were subjected to a standardized handling/restraint protocol in which blood samples were collected within 3 min, and again at regular intervals for 60 min. Analysis of blood samples revealed that both non‐breeding and breeding sparrows that were held in the traps had significantly higher baseline corticosterone than controls, and showed no further increase in corticosterone secretion in response to handling. However, corticosterone responses to trapping differed seasonally. Our study indicates that although birds did not exhibit prolonged escape behavior while trapped, entry into a walk‐in trap initiated a robust stress response. Taken together with data from a previous study, our data suggest that ornithologists should consider species‐specific and stage‐specific effects of trapping on physiology when designing field studies.     

Influence of researcher experience and fieldwork intensity on the probability of brood losses in sensitive species: The case of the Red-backed Shrike Lanius collurio

Minimizing disturbance to animals when studying them should be a major consideration in ecological research design, especially when species are known to be sensitive to disturbances. A basic method in the study of bird reproductive ecology involves nest visits, but these can adversely affect birds’ breeding success. Appropriate fieldwork procedures are therefore highly important, especially in the case of timid and sensitive species. This study aimed to assess the impact of the method of searching for nests of Red-backed Shrike Lanius collurio on the probability of these birds abandoning their broods. Our study revealed that observer experience and nest searching intensity did influence the likelihood of brood desertion by this species. Less field experience and a greater nest searching intensity caused the shrikes to abandon their nests more often. We recommend paying scrupulous attention to the behaviour of the birds when searching for nests and when looking for nests after incubation has started.     

Island accessibility and distance from beach influence nesting success of Sooty Falcons Falco concolor in Oman

Colonial island‐breeding birds can be particularly vulnerable to anthropogenic disturbance, which can adversely affect their nesting success. We studied Sooty Falcons Falco concolor breeding on 10 ground‐predator‐free islands in the Sea of Oman during 2007–2014 and evaluated spatio‐temporal trends in the number of breeding pairs occurring on the islands and the factors influencing nesting success. The number of breeding pairs on the islands declined during the study, due mostly to the decline on accessible islands; the rate of decline on islands accessible to humans was double that on inaccessible ones. The number of nests with one or more eggs declined during the study period, and the percentage of nests with eggs that produced one or more chicks showed an increasing trend over time. Sooty Falcon nests located farther away from beaches experienced a significantly higher probability of nesting success than those located closer to beaches. Our results suggest that the number of breeding Sooty Falcons on the islands of northern Oman is declining and that human disturbance may be a contributing factor; this probably mirrors the situation in other parts of the breeding range of this species.     

Nesting Success in Crimson Finches: Chance or Choice?

In avian systems, nest predation is one of the most significant influences on reproductive success. Selection for mechanisms and behaviours to minimise predation rates should be favoured. To avoid predation, breeding birds can often deter predators through active nest defence or by modifying behaviours around the nest (e.g. reducing feeding rates and vocalisations). Birds might also benefit from concealing nests or placing them in inaccessible locations. The relative importance of these strategies (behaviour vs. site selection) can be difficult to disentangle and may differ according to life history. Tropical birds are thought to experience higher rates of predation than temperate birds and invest less energy in nest defence. We monitored a population of crimson finches (Neochmia phaeton), in the Australian tropics, over two breeding seasons. We found no relationship between adult nest defence behaviour (towards a model reptile predator) and the likelihood of nest success. However, nest success was strongly related to the visibility of the nest and the structure of the vegetation. We found no evidence that adult nest building decisions were influenced by predation risk; individuals that re‐nested after a predation event did not build their nest in a more concealed location. Therefore, predator avoidance, and hence nest success, appears to be largely due to chance rather than due to the behaviour of the birds or their choice of nesting sites. To escape high predation pressures, multiple nesting attempts both within and between seasons may be necessary to increase reproductive success. Alternatively, birds may be limited in their nest‐site options; that is, high‐quality individuals dominate quality nest sites.     

Nest monitoring does not affect nesting success of Whinchats Saxicola rubetra

It is important to assess the effect that research activities may have on animals in the wild, especially when key parameters, such as breeding success, could potentially be influenced by observer activity. For birds, some studies have suggested that nest monitoring can increase the chances of nest failure due to predation, whereas others suggest that human nest visits may actually deter mammalian predators. Nest monitoring visits can also influence breeding success more indirectly by altering parental provisioning behaviour. Here, the influence of monitoring activities on nest success was examined in a ground‐nesting grassland bird, the Whinchat Saxicola rubetra. During the egg phase, a sample of nests were not visited between the initial finding event and the estimated hatching date; instead, the nest status was assessed at a distance. Daily survival rates (DSR) for these nests were compared with that of nests visited every 2 days. During the nestling phase, the effects of observer nest visits on parental provisioning behaviour were determined. Nest visits were found not to affect egg DSR significantly, and parental provisioning was disrupted for a maximum of 20 min (0.52% of the nestling period) following an observer visit. Given the variation in response to nest visits across species, we suggest that consideration should be given to observer impact in all studies where predation risk is high. Here, we illustrate a method for researchers to assess the impact of their nest visits to ensure they are not biasing estimates of breeding success.     

The impact of researcher disturbance on nest predation rates: a meta‐analysis

The effects of visits to nests by researchers interested in quantifying avian nesting success have received considerable attention, as researchers have long been concerned about the possible negative effects of their own activities on the resulting estimates. There is a widely held view that investigator disturbance has an overall negative effect on breeding success by increasing nest predation rates in the nests studied. However, to date no one has statistically assessed the empirical evidence for such a relationship. We undertook a meta‐analysis of published results to assess whether researcher activities increase nest predation in birds. We also assessed the variability in this effect in relation to the traits of the study species and the methodology used. These analyses used data from 18 experimental studies involving 25 species from six avian orders. Our results suggest that, contrary to the traditional view, researcher activities do not generally affect the incidence of nest predation. Moreover, this relationship appears inconsistent among avian orders and, surprisingly, nest survival of passerines increased weakly with researcher activities. We also found significant positive effects of researcher activity on nest survival for species breeding on coastal areas and for species nesting on the ground. The possible explanation for these differences among orders and guilds could be due to different nest predator communities. This new perspective on the effect of investigators could have important implications for bird management and conservation, as well as for other fields of study such as ecology and evolution, in which nest survival rates measured in the field are widely used to test and support a range of hypotheses.     

Negligible effects of blood sampling on reproductive performance and return rates of Tree Swallows

Blood sampling is a frequently used method of collecting genetic and physiological data in natural populations, and understanding the possible impact of blood sampling on individuals and populations is important, both for the welfare of study organisms and to avoid introducing bias into analyses using bled individuals. Most studies of birds have revealed minimal negative effects of blood sampling. However, Brown and Brown (2009. Auk 126: 853–861) found that blood sampling reduced return rates of Cliff Swallows (Petrochelidon pyrrhonota), suggesting that these results are not always generalizable and that swallows (Hirundinidae) may be particularly sensitive to blood sampling. We examined the possible effects of blood sampling on the reproductive performance of female Tree Swallows (Tachycineta bicolor) and the return rates of both females and offspring in a population in New York state. To reduce the chances of Type II error, we tested 15 possible effects of blood sampling on reproductive performance and return rates using generalized linear mixed models. Overall, our results suggest that blood sampling had few negative effects on within‐year reproductive success or survival of adult females. The one exception was that bleeding nestlings had a negative effect on the number of young that fledged in broods of five or six nestlings. Bleeding did not negatively impact return rates of females or nestlings in our Tree Swallow population. Our results support those of other studies suggesting that blood sampling has few negative effects on within‐year reproductive success or survival of adult females, and reiterate the importance of systematically testing for possible effects with datasets compiled over multiple years because such effects may be impossible to detect via direct monitoring during a single breeding season.     

Improvement of reproductive performance with age and breeding experience depends on recruitment age in a long‐lived seabird

Reproductive success increases with age in many species, however, the underlying mechanisms remain unclear and several hypotheses have been proposed to explain age‐related improvements in reproductive output. In this contribution we investigated the effects of age, recruitment age, breeding experience and sex on reproductive performance during the early breeding career in the common tern Sterna hirundo using long‐term individual‐based data. We used measurements of performance, which spanned the entire breeding process: clutch size, hatching success, fledging success and fledglings per pair. Longitudinal analyses within individuals showed a clear increase with age in all performance measures. Furthermore, a significant change in reproductive performance was found between first time‐ and experienced breeders. Recruitment age had a strong influence on hatching and fledging success: two‐year‐old recruits had significantly lower reproductive success than birds which recruited at older ages, but the increase in breeding performance with experience was stronger in young recruits. Comparing age and experience effects, age effects were more pronounced during the first breeding attempts, whereas experience effects were also visible in subsequent breeding attempts. The degree of intra‐individual improvements in reproductive performance is due to a complex interplay of age at first breeding and experience. The results strongly support the constraint hypothesis.     

Effects of military activity on breeding birds

United States military bases provide habitat for a diverse suite of wildlife species despite intense anthropogenic disturbance inherent in training activities. Little research has examined how military activity affects wildlife reproduction. We compared parental investment, reproductive success, offspring and adult quality, and stress hormone concentrations of northern cardinals (Cardinalis cardinalis) breeding in areas that differed 10-fold in levels of on-ground military activity. We found no evidence of direct impacts of military activity on cardinals, nor did the reproductive success of several other passerine species appear to be affected. However, we observed American crows (Corvus brachyrhynchos) much less frequently in areas of high military activity, and cardinals nesting in those areas were less responsive to crow models. The apparent displacement of this nest predator suggests that military activity could indirectly benefit some wildlife. Although these results are promising for the conservation of birds that depend on military bases for breeding habitat, further assessment of direct and indirect effects of military training on a wider array of species is required before concluding that such activity is benign. © 2012 The Wildlife Society.     

Effects of capture and video‐recording on the behavior and breeding success of Great Tits in urban and forest habitats

Behavioral research often involves capturing and video‐recording birds, but these procedures may have undesired effects on the behavior of birds that have rarely been quantified. In addition, birds in urban and more natural areas may differ in their sensitivity to disturbance. We examined the possible effects of both capturing, weighing and measuring, and taking a blood sample, and the presence of video‐cameras on the behavior of male and female Great Tits (Parus major) breeding in urban and forest habitats. Using a 2 × 2 block design, we compared the behavior and breeding success of parents that either were or were not captured on their nests a few days before behavioral observations, and of parents that either were or were not habituated to the presence of a concealed video‐recorder mounted on nest boxes. We found no significant effects of habituation to the camera on bird behavior, but males captured in their nest boxes were more vigilant and hesitated longer before entering nest boxes, and also had slightly lower provisioning rates than males that had not been captured. Captured females also tended to be more vigilant than females that had not been captured, but their provisioning rates were not affected. Capturing males also influenced the behavior of their non‐captured mates, but capturing females had no effect on the behavior of their non‐captured mates. We found no difference in the effects of capture on Great Tits in urban and forest habitats, and our treatments also had no effect on the mass, size, and survival of nestlings until fledging. Our results suggest that, for Great Tits, being captured results in sex‐dependent behavioral effects that can last for at least several days. As such, we suggest that the possibility of similar effects in other species of birds should be considered in behavioral studies where birds must be captured, and recommend either that behavioral data be collected before capturing birds or that all birds in a study should be captured and handled in a standardized way.     

Effect of Geolocators on Migration and Subsequent Breeding Performance of a Long-Distance Passerine Migrant

Geolocators are small light-weight data loggers used to track individual migratory routes, and their use has increased exponentially in birds. However, the effects of geolocators on individual performance are still poorly known. We studied geolocator effects on a long-distance migrating passerine bird, the northern wheatear (Oenanthe oenanthe L.). We asked the general question of whether geolocators affect migratory behaviour and subsequent reproductive performance of small passerines by comparing arrival time, breeding time, breeding success and survival of geolocator versus control birds of known identity and breeding history. During two years geolocator birds (n=37) displayed a lower apparent survival (30%) as compared to controls (45%, n=164). Furthermore, returning geolocator birds (n=12) arrived on average 3.5 days later, started laying eggs 6.3 days later, and had lower nest success (25%) than control birds (78%). Our results suggest that geolocators affect migratory performance with carry-over effects to the timing of breeding and reproductive success in the subsequent breeding season. We discuss the implications of such geolocator effects for the study of migratory strategies of small passerines in general and suggest how to identify and investigate such effects in the future.     

Nest positioning by male Daito White‐eyes Zosterops japonicus daitoensis improves with age to reduce nest predation risk

Age‐related improvement in reproductive success is widely observed in birds, and the mechanisms by which productivity is enhanced have received considerable attention. However, little is known about how parental age affects the loss of eggs or nestlings despite the fact that age effects on nesting success are often reported. We examined parental age effects on reproductive success in relation to the avoidance of nest predation in an island subspecies of the Japanese White‐eye, the Daito White‐eye Zosterops japonicus daitoensis. Clutch size and annual number of breeding attempts did not differ between parental age classes. Reproductive success was affected only by male age through an increase in nesting success. Nest failure was attributed only to predation in this species and nest concealment and nest height were important nest characteristics promoting successful fledging. Older males built their nests in more concealed and higher positions than first‐year birds, regardless of vegetation status around the nest. Analysis of individual birds suggested that by shifting the nest to a safer position, male White‐eyes achieved higher nesting success than in the previous year. Of three hypotheses of age‐related improvement in reproductive success considered, our data favoured the hypothesis that as individuals grow older, their breeding competence improves.     

Nesting Ecology of Boreal Forest Birds Following a Massive Outbreak of Spruce Beetles

Abstract: We studied breeding dark-eyed juncos (Junco hyemalis), yellow-rumped warblers (Dendroica coronata), and spruce-nesting birds from 1997 to 1998 among forests with different levels of spruce (Picea spp.) mortality following an outbreak of spruce beetles (Dendroctonus rufipennis) in Alaska, USA. We identified species using live and beetle-killed spruce for nest sites and monitored nests to determine how the outbreak influenced avian habitat selection and reproduction. We tested predictions that 1) nesting success of ground-nesting juncos would increase with spruce mortality due to proliferation of understory vegetation available to conceal nests from predators, 2) nesting success of canopy-nesting warblers would decrease with spruce mortality due to fewer live spruce in which to conceal nests, and 3) both species would alter nest-site selection in response to disturbance. Juncos did not benefit from changes in understory vegetation; nesting success in highly disturbed stands (46%) was comparable to that in undisturbed habitats throughout their range. In stands with low spruce mortality, nesting success of juncos was low (5%) and corresponded with high densities of red squirrels (Tamiasciurus hudsonicus). Yellow-rumped warblers nested exclusively in spruce, but success did not vary with spruce mortality. As disturbance increased, nesting warblers switched from selecting forest patches with high densities of live white spruce (Picea glauca) to patches with beetle-killed spruce. Warblers also placed nests in large-diameter live or beetle-killed spruce, depending on which was more abundant in the stand, with no differences in nesting success. Five of the 12 other species of spruce-nesting birds also used beetle-killed spruce as nest sites. Because beetle-killed spruce can remain standing for >50 years, even highly disturbed stands provide an important breeding resource for boreal forest birds. We recommend that boreal forest managers preserve uncut blocks of infested forest within managed forest landscapes and practice partial harvest of beetle-killed spruce rather than commercial clear-cutting of infested stands in order to sustain breeding bird populations until natural reforestation occurs. Because breeding densities do not always reflect fitness, assessing impacts of a massive natural disturbance should include measuring impacts of changes in vegetation on both reproductive success and predator-prey dynamics.