An inexpensive camera system for monitoring cavity nests

ABSTRACT A variety of pole‐mounted cameras have been developed for monitoring nest cavities. However, currently available camera systems may either be prohibitively expensive or difficult to assemble. I developed an inexpensive (<$500 US) and easily assembled camera system that allows researchers to monitor cavity nests from the ground. The system consists of a small camera, a cable connecting the camera to a ground‐level power source and laptop computer, and a flexible neck connecting the camera to a telescoping pole. During a study of Red‐headed Woodpeckers (Melanerpes erythrocephalus), I used this camera to inspect 16 nests and found that the images were clear and allowed accurate counts of eggs and nestlings. This camera system uses standard, off‐the‐shelf components, and can easily be altered. The design is not appropriate for humid or dense‐canopy environments because of the inclusion of a laptop and its wired design. However, this design makes the system inexpensive and allows researchers to save, edit, and view nest inspection recordings.     

An economical wireless cavity-nest viewer

ABSTRACT.   Inspection of cavity nests and nest boxes is often required during studies of cavity-nesting birds, and fiberscopes and pole-mounted video cameras are sometimes used for such inspection. However, the cost of these systems may be prohibitive for some potential users. We describe a user-built, wireless cavity viewer that can be used to access cavities as high as 15 m and with entrance diameters as small as 2.5 cm. System components include a wireless camera, boom with near-infrared lighting system, hand-held television, and telescoping pole. The unit can be assembled in about one day with commonly available tools, and the total cost was about $850 (US). Our cavity-viewing system was used to monitor the nests of Western Bluebirds ( Sialia mexicana ) and proved to be reliable and effective. During two field seasons, we attempted to check the status of nests 928 times and were able to determine the nesting stage 901 times (97%). For those willing to assemble their own units, our cavity viewer permits safe, direct examination of cavity nests or open nests for investigators with limited budgets.     

A novel nest‐monitoring camera system using a Raspberry Pi micro‐computer

The utility, availability, cost‐effectiveness, and reliability of prefabricated video systems designed to monitor wildlife have lagged behind the unique and varied needs of many researchers. Many systems are limited by inflexible video settings, lack of adequate data storage, and cannot be programmed by the user. More sophisticated systems can be cost prohibitive, and the literature describing remote wildlife video monitoring has, for the most part, not incorporated advances in camera and computer technology. Here, we present details of a pilot study to design and construct a lower cost (US $340) nest camera system to record the behavior of Acorn Woodpeckers (Melanerpes formicivorus) in artificial tree cavity nests. This system incorporates a Raspberry Pi micro‐computer, Pi NoIR infrared camera, a wireless adapter to transmit video over the Internet, and Deka rechargeable gel batteries for power. We programmed the system to motion‐sense, to record exclusively during daylight hours, and to automatically upload videos to the cloud over wireless Internet. The Raspberry Pi micro‐computer does not require advanced programming or electrical engineering skills to build and configure and, because it is programmable, provides unprecedented flexibility for field researchers who wish to configure the system to the specific needs of their study.     

Use of non-stop video surveillance to monitor breeding activity of primary cavity nesters in remote areas

I developed a video surveillance system to monitor breeding activity of primary cavity nesters in remote areas. A small video camera was installed inside a nesting cavity and I used wireless transmission of the video signal from the nest tree to a field station equipped with electricity to record behaviour. In a pilot study, I documented parental activities in a nest of the three-toed woodpecker (Picoides tridactylus). The female stayed with the chicks at night two times, whereas the male did this regularly. Adults did not always incubate or brood while on the nest but instead spent some time in motion. The described system is suitable for studying nesting behaviour of species living in remote areas with difficult access, because the proposed wireless transmission of the video signal minimizes manual operations at the nesting tree.     

Nest‐site selection by Slender‐billed Parakeets in a Chilean agricultural‐forest mosaic

ABSTRACT Species in the family Psittacidae may be particularly vulnerable to anthropogenic habitat transformations that reduce availability of suitable breeding sites at different spatial scales. In southern Chile, loss of native forest cover due to agricultural conversion may impact populations of Slender‐billed Parakeets (Enicognathus leptorhynchus), endemic secondary cavity‐nesting psittacids. Our objective was to assess nest‐site selection by Slender‐billed Parakeets in an agricultural‐forest mosaic of southern Chile at two spatial scales: nest trees and the habitat surrounding those trees. During the 2008–2009 breeding seasons, we identified nest sites (N= 31) by observing parakeet behavior and using information provided by local residents. Most (29/31) nests were in mature Nothofagus obliqua trees. By comparing trees used for nesting with randomly selected, unused trees, we found that the probability of a tree being selected as a nest site was positively related to the number of cavity entrances, less dead crown, and more basal injuries (e.g., fire scars). At the nesting‐habitat scale, nest site selection was positively associated with the extent of basal injuries and number of cavity entrances in trees within 50 m of nest trees. These variables are likely important because they allow nesting parakeets to minimize cavity search times in potential nesting areas, thereby reducing energetic demands and potential exposure to predators. Slender‐billed Parakeets may thus use a hierarchical process to select nest sites; after a habitat patch is chosen, parakeets may then inspect individual trees in search of a suitable nest site. Effective strategies to ensure persistence of Slender‐billed Parakeets in agricultural‐forest mosaics should include preservation of both individual and groups of scattered mature trees.     

Nest cavity orientation in black‐capped chickadees Poecile atricapillus: do the acoustic properties of cavities influence sound reception in the nest and extra‐pair matings?

Birds that nest in cavities may regulate nest microclimate by orienting their nest entrance relative to the sun or prevailing winds. Alternatively, birds may orient their nest entrance relative to conspecific individuals around them, especially if the acoustic properties of cavities permit nesting birds to better hear individuals in front of their nest. We measured the cavity entrance orientation of 132 nests and 234 excavations in a colour‐banded population of black‐capped chickadees Poecile atricapillus for which the reproductive behaviour of nesting females was known. Most chickadees excavated cavities in rotten birch Betula papyrifera, aspen Populus tremuloides and maple Acer saccharum. Nest cavities showed random compass orientation around 360° demonstrating that chickadees do not orient their cavities relative to the sun or prevailing winds. We also presented chickadees with nest boxes arranged in groups of four, oriented at 90° intervals around the same tree. Nests constructed in these nest box quartets also showed random compass orientation. To test the acoustic properties of nest cavities, we conducted a sound transmission experiment using a microphone mounted inside a chickadee nest. Re‐recorded songs demonstrate that chickadee nest cavities have directional acoustic properties; songs recorded with the cavity entrance oriented towards the loudspeaker were louder than songs recorded with the cavity entrance oriented away from the loudspeaker. Thus, female chickadees, who roost inside their nest cavity in the early morning during their fertile period, should be better able to hear males singing the dawn chorus in front of their nest cavity. Using GIS analyses we tested for angular‐angular correlation between actual nest cavity orientation and the azimuth from the nest tree to the territories and nest cavities of nearby males. In general, nest cavity entrances showed no angular‐angular correlation with neighbourhood territory features. However, among birds who followed a mixed reproductive strategy and nested in the soft wood of birch and aspen trees, nest cavity entrances were oriented towards their extra‐pair partners. We conclude that nest cavity orientation in birds may be influenced by both ecological and social factors.     

Social paper wasp (Agelaia pallipes) predates songbird nestling

The social paper wasp Agelaia pallipes is known to eat carrion and scavenge on vertebrates. There are few records of wasps predating vertebrates, including an attack on an adult hummingbird and the predation of bird nestlings. During a project monitoring reproductive behaviour of a neotropical songbird, the Lined Seedeater Sporophila lineola in south-eastern Brazil, we recorded the predation of a four-day-old nestling by a social paper wasp. In the video, the adult female bird attempted to visit the nest prior to the predation. The male could be seen with its crest feathers erect after a wasp left the nest, when the nestling was presumably already dead. When we arrived at the nest to remove the camera, we found the nestling dead, and did not observe the parents in the vicinity. We also registered two other dead nestlings in a different nest with similar wounds. However, the conclusive cause of death of those nestlings is unknown. Nest predation is a major selective pressure in birds, and insects are rarely assumed to play a notable role in this process. Further research is needed to better understand the nature of the relationship between wasps and birds.     

Do parents play a role in the timing and process of fledging by nestling Mountain Bluebirds?

What causes young birds to leave nests remains unclear for almost all altricial species. For many years, the assumption was that parents often controlled the time of fledging by coaxing young from nests, e.g., by holding food within view, but out of reach, of nestlings. This assumption, though, was based solely on scattered anecdotal reports of such behavior. We used continuous video‐recording of nests to assess the role of parents, if any, in the timing and process of fledging of cavity‐nesting Mountain Bluebirds (Sialis currucoides). We placed perches ~50 cm in front of nest‐box entrances to give parents ample opportunity to display food to nestlings. We found no evidence that parents routinely initiated the fledging process. On the day of fledging, parents did not perch on supplemental perches with food more often, or for longer periods of time, than on the day before fledging. Also, after going to nest‐box entrances, parents never held food away from a nestling reaching for the food. Parents were usually absent (16 of 19 cases) when the first nestling fledged. In the remaining three cases, a parent perched with food in view of a nestling for 8, 15 and 65 s, respectively, just before that nestling fledged. Although these might have appeared to be attempts at coaxing, in each case, the parent was encountering, for the first time, a nestling partially emerging from the nest entrance. Parents may simply have hesitated to approach nests because the nestling's position prevented parents from delivering food in the normal manner. Finally, the rate at which parents fed nestlings on the day of fledging did not differ from the rate the day before, suggesting that parents do not try to use hunger to induce fledging. Our results are consistent with previous research suggesting that, in Mountain Bluebirds, it is a nestling that initiates fledging, typically when it reaches some threshold state of development.     

Experimental study of alarm calls of the oriental tit (Parus minor) toward different predators and reactions they induce in nestlings

Anti-predatory strategies of birds are diverse and may include predator-specific alarm calls. For example, oriental tit (Parus minor) parents can distinguish snakes from other predators and produce snake-specific referential vocalizations ("jar" call) when a snake poses a threat to their nest. The “jar” call has a very specific function to induce fledging of nestlings close to fledging age. This reaction ensures nestlings' survival in natural encounters with snakes that are capable of entering nest cavities and kill entire broods. Sciurid rodents, like chipmunks, may pose a similar threat to cavity-nesting birds. We explored the hypothesis that parents use the fledging-inducing alarm vocalizations in this situation, because chipmunks, like snakes, can kill the brood upon entering the nest cavity. We compared alarm calls of parents toward two predators (chipmunk and snake) who pose a similar threat to the nestlings in a nest cavity, and toward an avian predator (Eurasian jay) who cannot enter nest cavities and poses no threat to the nestlings in a nest. Our results show that the vocal responses of oriental tits were different among the three predators. This suggests that the acoustic properties of vocal responses to predators are different between predators of a similar hunting strategy (nest-cavity entering). The playback of recorded vocal responses of parents to chipmunks did not trigger the fledging of old nestlings, whereas the vocalizations toward a snake did, as shown by earlier studies. Our study suggests that the vocal response of parents does not carry information about the ability of predators to enter the nest cavity and confirms the special status of alarm calls triggered by snakes.     

潜在洞巢资源差异对次级洞巢鸟及繁殖鸟类群落的影响

为了解次生林中潜在洞巢资源(包括各种啄木鸟的啄洞和人工巢箱)的多寡对次级洞巢鸟集团及繁殖鸟类群落结构的影响, 2007年11月至2008年7月, 我们在吉林省吉林市大岗林场选择洞巢密度不同的样地, 对其次级洞巢鸟及鸟类群落结构进行了比较研究。根据洞巢资源密度我们将9块样地分为3组, 即巢箱区(啄洞密度最低, 悬挂人工巢箱使其潜在洞巢资源总密度大幅提高)、低密度区(啄洞密度较低, 无巢箱)和高密度区(啄洞密度较高, 无巢箱), 调查了3组样地内鸟类的组成和密度、潜在洞巢资源的利用情况等。3组样地中均调查到4种初级洞巢鸟, 其种类组成略有不同; 4种次级洞巢鸟在3组样地广泛分布, 分别为白眉姬鹟(Ficedula zanthopygia)、大山雀(Parus major)、沼泽山雀(P. palustris)和普通鳾(Sitta europaea)。巢箱区和高密度区的次级洞巢鸟总密度显著高于低密度区。巢箱区同高密度区一样, 大山雀和白眉姬鹟的密度显著高于低密度区, 这是由于大山雀和白眉姬鹟是人工巢箱的主要利用鸟种, 而沼泽山雀和普通鳾的密度在三组样地间差异不显著。初级洞巢鸟总密度与啄洞密度、次级洞巢鸟总密度与潜在洞巢资源总密度都呈显著正相关关系。潜在洞巢资源丰富的样地中鸟类群落多样性指数显著高于潜在洞巢资源贫乏样地中的鸟类群落多样性指数, 人为增加洞巢资源可以改变鸟类群落组成并显著提高群落的多样性指数。三组样地中鸟类群落的均匀性、丰富度指数和种间相遇率没有显著差异, 群落相似性指数也相近。高密度区和低密度区鸟类群落集团结构相似。次级洞巢鸟密度的增加短时期内未对群落内其他主要鸟种的密度产生显著影响。研究结果显示, 初级洞巢鸟的密度决定了啄洞的丰富程度, 而洞巢资源的差异会对次级洞巢鸟集团的分布模式产生影响, 进而影响整个繁殖鸟类群落的结构。     

Dark tree cavities – a challenge for hole nesting birds?

Holes provide the safest nest sites for birds, but they are an underutilized resource; in natural forests there are usually more holes than birds that could use them. Some bird species could be prevented from nesting in holes because of their inability to operate in the low light conditions which occur in cavities. As no visual system can operate in complete darkness some nest cavities could be too dark to be useable even by hole‐nesters. Thus, the light conditions within tree cavities could constrain both the evolution of the hole nesting habit, and the nest site choice of the hole‐nesting birds. These ideas cannot be tested because little is known about the light conditions in cavities. We took an opportunity provided by ongoing studies of marsh tits Poecile palustris and great tits Parus major breeding in a primeval forest (Bia?owie?a National Park, Poland) to measure illumination inside their nest cavities. We measured illuminance in cavities at daybreak, which is just after the parents commenced feeding nestlings. Only ca 1% of incoming light reached the level of the nest. Illuminance at nests of both species (median = 0.1–0.2 lx) fell within mesopic‐scotopic range, where colour vision is impaired. Measurements in model cavities showed strong declines in illumination with distance from the entrance, with light levels typically as low as 0.01 lx at 40 cm from the cavity entrance. Thus cavities can be very dark, often too dark for the use of colour vision, and we suggest that ‘lighting’ requirements can affect the adoption of specific nest sites by hole nesting birds. We discuss implications of the findings for understanding the adaptations for hole‐breeding in birds.     

Clutch size relative to tree cavity size in Northern Flickers

We analysed clutch size versus nest size in 153 broods of the Northern Flicker Colaptes auratus , a woodpecker using natural cavities in British Columbia, Canada. Larger volume cavities were less susceptible to predation and cavity size was positively associated with the age and body size of males and with the body condition of female parents. Although clutches varied between 4 and 11 eggs, and the floor area of cavities varied about 5-fold, we found no relationship between clutch size and floor area or cavity volume. To see if there were fitness consequences to clutch size relative to nest size, we examined hatching success and nestling mortality in flicker broods. Hatching success was not related to cavity size, but crowding slightly reduced nestling survival even when clutch size was controlled statistically. However, there was no effect of cavity size on the total number of nestlings fledged. Newly excavated flicker cavities were smaller than reused cavities suggesting a cost to excavation. This cost, coupled with the minimal fitness consequences of overcrowding, may explain why flickers do not adjust clutch size to cavity size.     

Natural cavity restoration as an alternative to nest box supplementation

Nest box supplementation is widely used to increase nest‐site availability for cavity nesting animals but the analysis of its effects on individuals breeding in natural cavities is often neglected. This study offers a novel restoration technique to revert abandonment of natural breeding sites by a secondary cavity avian bird, the European roller (Coracias garrulus), and other ecologically similar species. We found that, after a program of nest box supplementation with ensuing monitoring, rollers gradually abandon nesting in natural and seminatural cavities in favor of nest boxes because the latter are of higher quality. We examine whether reducing the entrance size of natural and seminatural cavities improves their suitability for rollers. A 6‐year program reduced the diameter of the entrance of sandstone cavities and cavities in bridges. This led to a high occupancy (59%) of manipulated nest‐sites. Manipulated sites were most frequently occupied by rollers and little owls (Athene noctua) (31 and 18% of sites, respectively). Manipulation did not affect clutch size or fledgling success. We suggest that nest‐site diversity and nesting in natural cavities should be preserved to reduce nest box dependence. Our study illustrates the value of nest boxes when used alongside restoration of natural breeding sites and provides insights for the management of natural cavities.     

Selection of Nest Trees by Cavity‐nesting Birds in the Neotropical Atlantic Forest

One of the five most important global biodiversity hotspots, the Neotropical Atlantic forest supports a diverse community of birds that nest in tree cavities. Cavity‐nesting birds may be particularly sensitive to forestry and agricultural practices that remove potential nest trees; however, there have been few efforts to determine what constitutes a potential nest tree in Neotropical forests. We aimed to determine the characteristics of trees and cavities used in nesting by excavators (species that excavate their own nest cavity) and secondary cavity‐nesters (species that rely on existing cavities), and to identify the characteristics of trees most likely to contain suitable cavities in the Atlantic forest of Argentina. We used univariate analyses and conditional logistic regression models to compare characteristics of nest trees paired with unused trees found over three breeding seasons (2006–2008). Excavators selected dead or unhealthy trees. Secondary cavity‐nesters primarily selected cavities that were deep and high on the tree, using live and dead cavity‐bearing trees in proportion to their availability. Nonexcavated cavities suitable for birds occurred primarily in live trees. They were most likely to develop in large‐diameter trees, especially grapia Apuleia leiocarpa and trees in co‐dominant or suppressed crown classes. To conserve cavity‐nesting birds of the Atlantic forest, we recommend a combination of policies, economic assistance, environmental education, and technical support for forest managers and small‐scale farmers, to maintain large healthy and unhealthy trees in commercial logging operations and on farms.     

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.     

The relationship between introduced European Starlings and the reproductive activities of Mountain Bluebirds and Tree Swallows in British Columbia,Canada

The European Starling Sturnus vulgaris is an introduced species in North America and is an aggressive competitor for tree cavity nest‐sites. Starlings are commonly considered to influence nest‐site selection and reproductive success of native cavity‐nesting species negatively. We examined the relationship between Starling nest density and the fecundity of two native secondary cavity‐using passerines, Mountain Bluebird Sialia currucoides and Tree Swallow Tachycineta bicolor. We monitored a total of 622 nests (approximately equal numbers for each of the three species) in woodpecker‐excavated and naturally occurring cavities in 29 small forest groves in central British Columbia, Canada, between 2000 and 2009. The dimensions of cavities used and the timing of nest initiation overlapped for all species, although Starlings initiated clutches earliest. Mixed‐effects models were used to assess whether nest abundance, clutch size or nest success were affected directly by Starling nest abundance, or indirectly via a shift in cavity selection or timing of breeding. Starlings and Mountain Bluebirds showed inverse trends in nest abundance. Mountain Bluebird clutch sizes were smaller if they were initiated later in the breeding season. There was weak evidence that Tree Swallow clutch size decreased with cavity depth when Starling nests were abundant, and increased with cavity depth where there were few Starling nests. We conclude that despite the aggressive nature of this exotic cavity‐nester, the influence of Starlings on native secondary cavity‐nesting passerines is modest where cavities are abundant.     

Validating the use of temperature data loggers to measure survival of songbird nests

ABSTRACT.   Accurate determination of nest fates and nest predators is possible through continuous video monitoring, but such monitoring is relatively expensive and labor intensive. If documenting of the timing of nest termination events is sufficient, then data loggers (DL) may allow more extensive sampling and may represent a viable alternative. I validated temperature DL records of nest survival time by simultaneous videotaping and compared results derived from DL records with those obtained by regular nest visits by an observer. I estimated the fate of 937 nests of nine species of open cup-nesting songbirds, including 673 nests monitored using DL, 165 monitored using video cameras, 33 validation nests monitored simultaneously using both DL and video cameras, and 132 control nests monitored only by observer visits. Deployment of DL did not negatively influence nest survival rate. DL reliably recorded survival time and allowed classification of nest fates based on the potential fledging age, regardless of the frequency of nest visits by an observer. The true fate of nests that survived beyond the potential fledging age can not be safely determined from time of failure, except for nocturnal events that suggest partial predation. Video revealed frequent partial or complete predation on nests with old nestlings that would have been categorized as successful by other methods. I conclude that temperature DL are efficient, reliable, and relatively inexpensive tools for recording exact nest survival times and classification of nest fates, with implications for nest survival modeling and discriminating between diurnal and nocturnal predation.     

The discovery of hatching and transition to feeding young by male Mountain Bluebirds

In many bird species, only females incubate the eggs, but both sexes feed nestlings. The means by which males of such species discover hatching and transition to feeding their offspring remains almost completely unexplored. Of particular interest are species with nests whose contents are concealed from view. During June and early July 2015 in the Bighorn Mountains of Wyoming, we used continuous video‐recording of nests of cavity‐nesting Mountain Bluebirds (Sialia currucoides) to document the transition to feeding young by males. We saw no evidence that females used distinct vocal or visual displays to signal hatching to males. Observing mates carrying eggshells away from, or food into, nest boxes did not appear to trigger provisioning by males. Rather, at all 24 nests observed, males did not begin feeding until they had come to nest boxes and presumably sensed the presence of hatchings directly. Individual males varied, however, in both the manner in which they inspected nest contents and the number of times they did so before starting to feed young. Although most males fully entered nest boxes where they could see, touch, hear, and possibly smell hatchlings (or eggshell parts), other males may have detected hatchlings only by sound or possibly smell while perched at a nest‐box entrance. Based on past studies of mice and doves, we suggest that, for provisioning behavior to begin, some kind of direct sensation of offspring may be necessary to activate relevant neurons in the medial preoptic area of the hypothalamus of males, an area of the brain important in parental care. Additional research is necessary to test this, and to examine the effects of factors such as hormone levels and breeding experience on the means and rapidity by which males discover hatching and transition to nestling provisioning.     

Projected Availability of Natural Cavities for Wood Ducks in Southern Illinois

Abstract: Wood ducks (Aix sponsa) and other species use tree cavities in forested wetlands and adjacent upland forests for nest sites and cover. The availability of tree cavities suitable for nesting is important to the population dynamics of hole-nesting species, but there is little quantitative information on how forest succession and maturation affect densities of suitable nest sites in eastern deciduous forests. Several studies have measured availability of tree cavities for nesting wood ducks, but data on cavity formation and persistence rates are needed to model changes in cavity abundance. We measured abundance and persistence of tree cavities suitable for nesting wood ducks in southern Illinois, USA, during 1993-2002. We simulated changes in abundance of nest cavities in the Mississippi River floodplain and adjacent upland forests using estimates of tree cavity densities by tree-diameter size classes and 10-year cavity persistence rates by tree species. Cavities were disproportionately common in the largest size classes, but tree species varied in their propensity to form cavities. Beech (Fagus grandifolia; 0.41 cavities/tree) and sycamore (Plantanus occidentalis; 0.50 cavities/tree) were prolific cavity producers, whereas a small proportion (0.05 cavities/tree) of cottonwoods (Populus deltoides) contained cavities. Kaplan-Meier estimates of annual and 10-year cavity persistence averaged 0.95 and 0.64, respectively. Cavity persistence also differed among species (P = 0.02): cottonwoods had the lowest (0.54) and sycamores had the highest (0.89) 10-year tree cavity persistence rates. Tree fall (50.0%), cavity floor deterioration (37.5%), and narrowing of the cavity entrance (12.5%) were the most prevalent causes of tree cavity loss. Forest stand projections indicated that cavity abundance will increase up to 34% over recent levels during the first 10 years and by 44% after 50 years. Most of this increase will be contributed by tree species that are not commonly used by wood ducks, but cavities will increase in oaks (Quercus spp.) and beeches as the forest matures into cavity-bearing size classes. Sycamores will steadily contribute cavities, but cottonwood is predicted to provide fewer cavities due to low survival of cavity-bearing size classes. Our results suggest that availability of nest and den sites for cavity-dependent wildlife will increase as eastern deciduous forests mature over the next half century. Cost-effectiveness of artificial nest box programs should be reevaluated in light of projected changes in tree cavity availability as deciduous forests mature in the eastern United States.     

INVESTIGATION ON THE CAPE GANNET

Most Cape Parrot, Poicephalus robustus, nests have been recorded in snags (standing dead trees) making monitoring of nest contents and nest activities difficult and dangerous. Here the breeding activity of a Cape Parrot pair in the cavity of a live Henkell's Yellowwood (Podocarpus henkellii) is presented. Four eggs were laid in early-August and three chicks successfully raised. Incubation period was estimated at 30–32 days. Two nestlings fledged successfully and one (the youngest) was removed because it was injured in the nest and would not have survived. Fledging period was estimated at 80 days.