Addition Of Nest Boxes Research Articles

Environmental cues and dietary antioxidants affect breeding behavior and testosterone of male European starlings (Sturnus vulgaris)

Environmental cues, such as photoperiod, regulate the timing of major life-history events like breeding through direct neuroendocrine control. Less known is how supplementary environmental cues (e.g., nest sites, food availability) interact to influence key hormones and behaviors involved in reproduction, specifically in migratory species with gonadal recrudescence largely occurring at breeding sites. We investigated the behavioral and physiological responses of male European starlings to the sequential addition of nest boxes and nesting material, green herbs, and female conspecifics and how these responses depend on the availability of certain antioxidants (anthocyanins) in the diet. As expected, cloacal protuberance volume and plasma testosterone of males generally increased with photoperiod. More notably, testosterone levels peaked in males fed the high antioxidant diet when both nest box and herbal cues were present, while males fed the low antioxidant diet showed no or only a muted testosterone response to the sequential addition of these environmental cues; thus our results are in agreement with the oxidation handicap hypothesis. Males fed the high antioxidant diet maintained a constant frequency of breeding behaviors over time, whereas those fed the low antioxidant diet decreased breeding behaviors as environmental cues were sequentially added. Overall, sequential addition of the environmental cues modulated physiological and behavioral measures of reproductive condition, and dietary antioxidants were shown to be a key factor in affecting the degree of response to each of these cues. Our results highlight the importance of supplementary environmental cues and key resources such as dietary antioxidants in enhancing breeding condition of males, which conceivably aid in attraction of high quality females and reproductive success.

The Unknown Life of Floaters: The Hidden Face of Sexual Selection

Summary. Sexual selection, as a form of social selection based on reproductive resources, is a crucial driver of evolutionary change. Many studies on sexual selection identify potential targets only within the reproductive fraction of populations. Floaters constitute the non-territorial fraction of the population, according to the usual definitions. Floaters have been identified through exhaustive capture and marking programmes, removal and nest-box addition experiments, extra-pair paternity studies, acoustic marking and genetic studies. The literature shows that floaters may represent a considerable fraction of populations, especially among males. There is no clear evidence that size, condition or testosterone level is necessary for explaining floater status generally. However, the literature suggests that ornament size and expression are involved in territorial exclusion and may be either its cause or one of its consequences. There is some evidence that floaters survive and reproduce less well than terr...

Pre- and post-experimental manipulation assessments confirm the increase in number of birds due to the addition of nest boxes.

Secondary cavity nesting (SCN) birds breed in holes that they do not excavate themselves. This is possible where there are large trees whose size and age permit the digging of holes by primary excavators and only rarely happens in forest plantations, where we expected a deficit of both breeding holes and SCN species. We assessed whether the availability of tree cavities influenced the number of SCNs in two temperate forest types, and evaluated the change in number of SCNs after adding nest boxes. First, we counted all cavities within each of our 25-m radius sampling points in mature and young forest plots during 2009. We then added nest boxes at standardised locations during 2010 and 2011 and conducted fortnightly bird counts (January–October 2009–2011). In 2011 we added two extra plots of each forest type, where we also conducted bird counts. Prior to adding nest boxes, counts revealed more SCNs in mature than in young forest. Following the addition of nest boxes, the number of SCNs increased significantly in the points with nest boxes in both types of forest. Counts in 2011 confirmed the increase in number of birds due to the addition of nest boxes. Given the likely benefits associated with a richer bird community we propose that, as is routinely done in some countries, forest management programs preserve old tree stumps and add nest boxes to forest plantations in order to increase bird numbers and bird community diversity.

Enriching small trees with artificial nest boxes cannot mimic the value of large trees for hollow‐nesting birds

Large trees support unique habitat structures (e.g. hollows) that form over centuries and cannot be provided by small trees. Large trees are also declining in human‐modified landscapes worldwide. One restoration strategy gaining popularity involves adding nest boxes to smaller trees to replicate natural hollows. However, limited empirical research has tested how hollow‐nesting fauna responds to the presence of nest boxes. We asked: can the addition of nest boxes increase tree visitation by hollow‐nesting birds? We conducted a before‐after control‐impact (BACI) experiment using 144 nest boxes and 96 sample trees comprised of three sizes (small [20–50 cm dbh], medium [51–80 cm], and large [>80 cm]) and located in four landscape contexts (reserves, pasture, urban parklands, and urban built‐up areas). We recorded a significant increase in hollow‐nesting bird abundance and richness at large trees after nest box additions. However, the same response was not observed at medium, small, or control trees. We also recorded nonsignificant increases in hollow‐nesting bird abundance and richness at trees in modified landscapes after nest box additions compared to trees in reserves and control trees. Our results suggest that adding nest boxes to smaller‐sized trees may not attract hollow‐nesting birds. Therefore, nest box management strategies may require re‐evaluation as it is often assumed that hollow supplementation will attract hollow‐using fauna and sufficiently ameliorate the loss of large, hollow‐bearing trees. We advocate that large tree retention remains crucial and should be prioritized. Large trees could be effective target structures for habitat restoration, especially in modified landscapes.

Do Hole-Nesting Passerine Birds Fare Well at Artificial Suburban Forest Edges?

Urbanization and subsequent disturbance, habitat alteration and fragmentation are usually seen as major threats to biodiversity. However, habitat alterations might also create new habitat types that can be used by the local fauna. Here, we tested whether hole-nesting passerines use forest edges next to open grassland areas for reproduction by assessing five golf courses in the Helsinki region in southern Finland. We found a major effect in all species breeding at our sites (great tit, Parus major; blue tit, Cyanistes caeruleus; pied flycatcher, Ficedula hypoleuca): both nest occupancy and the number of offspring were significantly higher at the artificial edges than 50 m into the original forests. We conclude that man-made suburban forest edges provide suitable habitat for nesting, which could be further improved with the addition of nest boxes.

Responses to experimental reduction and increase of cavities by a secondary cavity-nesting bird community in cavity-rich Pyrenean oak forests

Cavity shortage limits secondary cavity-nesting birds (SCN) assemblages in intensively-managed forests with few cavities, but whether cavity availability limits SCN in cavity-rich forests remains unclear. To address this issue, we used a replicated before-after-control-impact design in which the availability of cavities was experimentally reduced and increased in cavity-rich Quercus pyrenaica forests. Cavity-blocking and nest-box addition led to reduction by 66% and increase by 185%, respectively, of nest densities of blue (Cyanistes caeruleus) and great (Parus major) tits. Analysis of cavity characteristics suggests that tits occupied less suitable cavities in blocking plots compared to control and nest-box addition plots after treatments, further indicating that the availability of suitable nest-sites may limit tit populations. No effect of cavity manipulation was found for short-toed treecreepers (Certhia brachydactyla) and Eurasian nuthatches (Sitta europaea), which defend larger territories than tits and whose numbers may be more influenced by territoriality than by nest-sites. Alternatively, high plasticity in nest-site use of treecreepers may enable them to cope with reductions in cavity availability and increased interspecific competition. Spotless starlings (Sturnus unicolor) were little affected by cavity manipulation. Often foraging on pastures, starlings may be more limited through reduced foraging opportunities in this forested landscape than by nest-sites. In addition, starlings may exclude other species from their preferred cavities to cope with reductions in numbers of suitable cavities. Community responses to the variation in cavity abundance in cavity-rich Pyrenean oak forests may therefore vary considerably among species, depending on their plasticity in nest-site use, behavioral dominance, foraging conditions or social structure. Thus, management actions aimed to increase cavity abundance and suitability for SCN communities in cavity-rich forests should consider inter-specific interactions and species-specific characteristics of the targeted species.

Experimental test of nest‐site limitation in mature mixed forests of central British Columbia, Canada

AbstractNest‐site availability limits cavity‐using populations in many harvested forests; however, little is known about the extent of nest‐site limitation in mature forests with a full complement of excavator species and intact processes of cavity creation and loss. To examine the role of nest‐site availability in limiting cavity‐using populations in mature mixed conifer forests in central British Columbia, Canada, we conducted an 11‐year before‐after control‐impact experiment in which we increased nest‐site availability via nest box addition. Our 7 sites (3 treatments, 4 controls) had low cavity densities (<2/ha) prior to treatment and cavity occupation rates were also low (<10%/yr), which is a relationship often cited in the literature as evidence of non‐limitation in cavity‐nesting populations. Following nest box addition at our treatment sites, which tripled the availability of cavities, total density of bird and mammal nests more than tripled. Density of mountain chickadee (Poecile gambeli) nests increased 9‐fold on treatment sites and returned to pre‐treatment levels following box removal, suggesting that chickadee populations were limited by cavity availability at our study sites. Density of red squirrel (Tamiasciurus hudsonicus) and northern flying squirrel (Glaucomys sabrinus) nests and roosts also increased significantly at treatment sites following box addition and declined following box removal. We noted little change in chickadee or squirrel nest density at control sites monitored concurrently. Squirrels preferred large‐sized over small‐sized boxes, and significantly enlarged the entrance areas of small boxes by chewing, suggesting that there may have been a shortage of suitable nest and roost sites for them in our study area. We contend that low cavity occupancy rates may not accurately reflect nest‐site availability for cavity nesters in mature forests, and that cavity size may influence the true availability of cavities on the landscape. © 2011 The Wildlife Society.

Supply of tree-holes limits nest density of cavity-nesting birds in primary and logged subtropical Atlantic forest

Tree cavities are proposed to limit populations and structure communities of cavity-nesting birds. Although the greatest diversity of cavity-nesting birds is found in tropical and subtropical moist forests, little is known about how tropical logging affects the abundance of cavities or cavity-nesting birds. We compared the abundance of cavities and cavity nests between primary and selectively-logged subtropical moist Atlantic forest in Argentina, and conducted the first before-after controlled nest-box addition experiment to determine whether nest sites limit the breeding density of cavity-nesting birds in tropical or subtropical moist forest. Visual inspection of 86 cavities identified through ground-surveys revealed that only 19% were suitable for nesting birds, suggesting that cavity abundance may be overestimated in the literature on tropical forests. Suitable cavities were found in fewer than 1% of 1156 trees <60 cm dbh but 20% of 20 trees >100 cm dbh. Logged forest had half the basal area of primary forest, one third the density of large trees, nine times fewer cavities suitable for nesting birds, and 17 times fewer active nests. When we added nest boxes, nesting density increased on treatment plots but not on control plots in both logged and primary forest, suggesting that cavity supply can limit nest density even in relatively undisturbed forest. This is the first experiment to show how reduced cavity supply in logged tropical forest can limit breeding density of cavity-nesting birds. International initiatives such as forest certification should promote tropical timber management strategies that conserve large live cavity-bearing trees.

Provision of nestboxes raises the breeding density of Great Tits Parus major equally in coniferous and deciduous woodland

Nestbox provision is a technique used to increase nest‐site availability for secondary cavity‐nesting birds. However, little is known about the demographic consequences of nestbox provision in different habitat types. To assess how nestbox provision affects the density of hole‐nesting birds simultaneously in two contrasting habitats, we compared the breeding density of Great Tits along transects without nestboxes with that in transects where nestboxes were provided. Although the initial density of breeders was considerably higher in the deciduous habitat than in the coniferous habitat, provision of nestboxes increased density by a similar number of additional pairs in each habitat type. Thus, the provision of nestboxes in managed coniferous forests may be as effective in increasing the breeding opportunities of cavity nesters as in deciduous stands. Moreover, previous research showed that pairs in deciduous habitat with nestboxes have consistently lower breeding success than those in coniferous habitat with nestboxes. It is possible that the addition of nestboxes in the preferred habitat increased density to such an extent that density‐dependent effects became apparent.

NESTING SUCCESS OF WESTERN BLUEBIRDS (SIALIA MEXICANA) USING NEST BOXES IN VINEYARD AND OAK-SAVANNAH HABITATS OF CALIFORNIA

Abstract Loss of oak woodlands to vineyard development in California is a growing concern to conservationists. Analyzing breeding performance of birds that nest in and around vineyards versus those that nest in nearby native habitat can provide information on the suitability of vineyard environments to birds. We placed predator-protected nest boxes in vineyard and oak-savannah habitats and monitored nest-box occupancy, nesting success, and life history characteristics of Western Bluebirds (Sialia mexicana) that used the boxes. Western Bluebirds were common occupants in both habitats, occupying >50% of available nest boxes. Analysis using program MARK revealed that nest survival was not associated with habitat type; however, clutch size was greater and nests were initiated earlier in vineyard than in oak-savannah habitat. Our results suggest that when naturally occurring nest sites are limiting, vineyards could be converted to good breeding habitat for Western Bluebirds with the addition of nest boxes. Nes...

Nest Boxes Reduce Flying Squirrel Use of Red-Cockaded Woodpecker Cavities

Abstract Reproductive success of red-cockaded woodpeckers (Picoides borealis) appears to be reduced when even a single cavity in a cluster of woodpecker cavities is occupied by a southern flying squirrel (Glaucomys volans). One potential technique for reducing flying squirrel use of woodpecker cavities is the addition of nest boxes to clusters. In this study we evaluated the effects of nest boxes and red-cockaded woodpecker presence (activity) on flying squirrel use of cavities at the Joseph W. Jones Ecological Research Center in Newton, Georgia from 26 September 2002 until 26 June 2003. The interaction between presence of nest boxes and woodpecker activity significantly affected success (proportion of time no flying squirrels occupied any cavities in a cluster; F1,16 = 5.10, P = 0.04). Success was higher in active clusters with nest boxes (95%) than active clusters without nest boxes (83%) but was similar in inactive clusters (success with and without nest boxes = 78%). The proportion of cavities usurped...

Nest‐site limitation and density dependence of reproductive output in the common goldeneyeBucephala clangula: implications for the management of cavity‐nesting birds

Summary Hole‐nesting birds are frequently faced with a shortage of suitable nest sites in regions of intensive forest management. Nest boxes are sometimes provided to alleviate nest‐site limitation in cavity‐nesting waterfowl and are also recommended for several rare and endangered species. However, the impacts on effective breeding numbers and breeding success have rarely been considered, particularly in instances where density dependence might operate. We experimentally manipulated nest sites to assess limits on the population size of a secondary cavity‐nesting species, the common goldeneyeBucephala clangula, living on freshwater lakes. We also examined density dependence in their reproductive output. Breeding pairs were counted in experimental and control areas over a 12‐year period; for 4 years (1988–91) before nest box addition (1992–94 in the experimental area) and for 5 years (1995–99) afterwards. Broods were counted each year between 1988 and 1999 to study reproductive output. Mean number of pairs per lake increased after the addition of nest boxes in the experimental area but not in the control area. However, neither the mean number of broods per lake nor the mean number of fledged birds per lake increased significantly in the experimental area. When the whole period of 1988–99 was considered and data pooled from all the lakes, the numbers of broods and fledged birds showed negative density dependence of reproductive output. Our results indicate that nest sites limit the population size of breeding common goldeneye, but show also that density‐dependent factors operate to limit reproductive output. The possibility that density dependence may negate management actions directed at increasing breeding numbers in cavity‐nesting waterfowl should be considered carefully before taking these actions. This also applies to nest box provisioning programmes aiming to manage populations of endangered species.

Social constraints on the onset of incubation in a neotropical parrot: a nestbox addition experiment

We examined whether the early onset of incubation serves to protect eggs from the dangers imposed by conspecifics in the green-rumped parrotlet,Forpus passerinus, a small neotropical parrot that lays a large clutch and begins incubation on the first egg. Nestboxes with eggs were installed and their fate was followed for 72h to determine whether egg destruction and nest site take-overs occurred as predicted by the Egg Protection and Limited Breeding Opportunities Hypotheses, or whether additional eggs appeared in the boxes as predicted by the Brood Parasitism Hypothesis. Eggs were destroyed at 40.6% of 69 experimental boxes but at only 4.5% of control nests occupied by laying pairs. No eggs were laid in the experimental boxes. Egg destruction at experimental nests occurred during daylight hours and all mortality was caused by green-rumped parrotlets. Over 75% of the nests were destroyed by male–female pairs prospecting for nest sites, and the remainder were destroyed by male–male pairs. Lone males never destroyed eggs, although they frequently visited experimental boxes. Two of three failures at control nests were the result of nocturnal predators, and the other nest was apparently destroyed by parrotlets. There was no significant difference between experimental and control boxes in the frequency of visitations by lone males, male–female pairs and male–male pairs. Although experimental boxes that parrotlets visited were discovered quickly after placement, parrotlets were usually slow to enter them (X=5.8h after discovery, range 0.3–23.5h). Control nests were rarely left unattended: females spent nearly 75% of their time in the box, and pairs were typically absent for short intervals (median=7.5min). Control females responded to intruding parrotlets by remaining in the box 94% of the time when alone, whereas males actively displaced and chased intruding parrotlets 66% of the time. Parrotlets that visited control nests approached the box significantly less often than those visiting experimental boxes. To ensure the survival of eggs, parrotlet parents must begin incubating eggs or guarding nests soon after laying to minimize destruction of clutches, loss of nest sites, a decline in the viability of their eggs and the time that all nestlings are exposed to predators.

A Comparison of the Breeding Ecology of Birds Nesting in Boxes and Tree Cavities

ABSTI~ICT.-We compared laying date, nesting success, clutch size, and productivity of four bird species that nest in boxes and tree cavities to examine whether data from nest boxes are comparable with data from tree cavities. Western Bluebirds (Sinlin nrexicnnn) gained the mast advantage from nesting in boxes. They initiated egg laying earlier, had higher nesting success, lower predation rates, and fledged marginally more young in boxes than in cavities but did not have laracr clutches or hatch more eggs. Plain Titmice (Pnnis iriorrmtrrs) nesting earlier in boxes. ~oise Wrens (~roglo&tes ~eiion) nesting in boxes laid larger clutches, hatched more eggs, and fledged mare young and had marginally higher nesting success and lower predation rates. Ash-throated Flycatchers (Myinrclirrs cincmscens) experienced no apparent benefits from ncsting in bows versus cavities. No significant relationships were found between clutch size and bottom area or volume of cavities for any of these species. These results suggest that researchers should use caution when extrapolating results from nestbox studies of reproductive success, predation rates, and productivity of cavity-nesting birds. Given the different responses of these four species to nesting in boxes, the effects of the addition of nest boxes on community structure also should be considered. Rrcrived 19 September 1996, nccepted 21 April 1997. NEST BOXES MAY BE USED AS A CONSERVATION

Landscape Modification and Patch Selection: The Demography of Two Secondary Cavity Nesters Colonizing Clearcuts

Current forestry practices radically modify habitat, particularly by increasing the frequency of early sera! stages. We examined the demography of two secondary cavity nesters, the Mountain Bluebird (Sialia currucoides) and the Tree Swallow (Tachycineta bicolor), with respect to landscape changes. The study area contained a mosaic of clearcuts ranging from 3 to 27 years in age. The initial distribution of both species was uneven with respect to patch age. Experimental addition of nest boxes: (1) increased the number of nesting pairs of both species, and (2) expanded the age range of occupied patches. Nest-site availability was the primary limiting factor in young patches, but vegetation structure was increasingly important in determining occupation in older patches, Mountain Bluebird patch occupation and Tree Swallow density were best predicted by the proportion of trees 1 to 3m in height. Although some patches contained multiple pairs of Mountain Bluebirds in natural cavities, experimental patches typically contained no more than one pair, even though excess nest boxes were available. The presence of nonbreeding floaters was an indication of nest-site limitation and suggested that Mountain Bluebirds sometimes defer breeding attempts rather than nest close to conspecifics. At low densities, Tree Swallows also were over-dispersed, but pairs saturated available nest boxes as density increased. Clutch size and number of chicks fledged from successful nests did not vary with patch age for either species, although swallows initiated clutches later in younger compared with older patches. Nest predation varied consistently with patch age; mean nest predation for both species was 86% (n = 30 pairs) in the youngest patches, 37% (n = 34) in mid-age patches, and 25% (n = 22) in the oldest patches. The low densities of both species in older patches was not associated with low productivity, suggesting that habitat selection occurred independently of potential productivity in this novel habitat.

Clutch size and nesting sites of the Mandarin DuckAix galericulata

The Mandarin Duck had a highly variable clutch size in both natural nest sites (tree cavities) and artificial sites (nest boxes); some very large clutches were recorded. The provision of artificial sites did not alter the size of clutches incubated in natural nest sites. However, the clutches incubated in artificial sites were smaller than those from natural sites when both were available. The addition of nest boxes to the study area substantially increased the total number of eggs incubated each year simply by the number of additional eggs incubated in boxes. Some nest sites, both natural and artificial, were unused in any one year. More than a quarter of clutches, both from natural and artificial nest sites, were never incubated; these were similar in size to clutches of incubated eggs. It is concluded that variability in clutch size resulted from intraspecific nest parasitism, and that the provision of artificial nest sites made little difference to the occurrence of this behaviour.