Red-cockaded Woodpecker Cavities Research Articles

UAS-Based Real-Time Detection of Red-Cockaded Woodpecker Cavities in Heterogeneous Landscapes Using YOLO Object Detection Algorithms

In recent years, deep learning-based approaches have proliferated across a variety of ecological studies. Inspired by deep learning’s emerging prominence as the preferred tool for analyzing wildlife image datasets, this study employed You Only Look Once (YOLO), a single-shot, real-time object detection algorithm, to effectively detect cavity trees of Red-cockaded Woodpeckers or RCW (Dryobates borealis). In spring 2022, using an unmanned aircraft system (UAS), we conducted presence surveys for RCW cavity trees within a 1264-hectare area in the Sam Houston National Forest (SHNF). Additionally, known occurrences of RCW cavity trees outside the surveyed area were aerially photographed, manually annotated, and used as a training dataset. Both YOLOv4-tiny and YOLOv5n architectures were selected as target models for training and later used for inferencing separate aerial photos from the study area. A traditional survey using the pedestrian methods was also conducted concurrently and used as a baseline survey to compare our new methods. Our best-performing model generated an mAP (mean Average Precision) of 95% and an F1 score of 85% while maintaining an inference speed of 2.5 frames per second (fps). Additionally, five unique cavity trees were detected using our model and UAS approach, compared with one unique detection using traditional survey methods. Model development techniques, such as preprocessing images with tiling and Sliced Aided Hyper Inferencing (SAHI), proved to be critical components of improved detection performance. Our results demonstrated the two YOLO architectures with tiling and SAHI strategies were able to successfully detect RCW cavities in heavily forested, heterogenous environments using semi-automated review. Furthermore, this case study represents progress towards eventual real-time detection where wildlife managers are targeting small objects. These results have implications for more achievable conservation goals, less costly operations, a safer work environment for personnel, and potentially more accurate survey results in environments that are difficult using traditional methods.

Do Red-cockaded Woodpecker (Dryobates borealis) cavity locations provide olfactory concealment from predators?

Nest site selection is crucial for survival and fecundity of birds. Predators find nests using visual, aural, thermal, and olfactory cues, yet few studies have evaluated olfactory concealment of nests. Rat snakes (Pantherophis spp.) are common nest predators that use ground-level olfactory cues to detect nest locations. In Arkansas, USA, we evaluated if cavity locations of the Red-cockaded Woodpecker (Dryobates borealis, RCW), a species that experiences nest predation by rat snakes, were associated with airflow conditions known to provide olfactory concealment for other bird species. We used a 3-dimensional sonic anemometer to measure ground-level air velocity, turbulence, and turbulence intensity at cavity trees and unused trees, and at cavity and opposite orientations on trees. For all airflow variables, we found no differences between used and unused trees and orientations. Other factors such as landscape-scale vegetation cover, forest stand structure, and tree characteristics may be more important for providing visual concealment or optimal foraging conditions. However, it remains possible that such factors also convey olfactory concealment. For example, savannah-like forests preferred by RCWs may have greater air turbulence than closed forests. Further research on RCWs and other bird species to address additional aspects of olfactory concealment, and relationships between different dimensions of concealment (e.g., between visual and olfactory concealment), would give insight into how habitat management could provide multiple benefits to birds.

Aggregations of Polistes Wasps Over-Wintering in Artificial Red-Cockaded Woodpecker Cavities

We document blockage of artificial Dryobates borealis (Red-cockaded Woodpecker) cavities by family Sphecidae (mud daubers) and large mixed-species aggregations of wintering Polistes (paper wasps) in cavity inserts at Great Dismal Swamp NWR in southeast Virginia. The large aggregations that we encountered are the only known cases of more than 2 paper wasp species cohabitating. Activity of Red-cockaded Woodpeckers within a cluster lessened the likelihood that paper wasps will aggregate in cavities, but not the likelihood that mud daubers will nest in cavities. The moist and saturated soils that predominate our field site may explain why these insects are more abundant compared to drier, upland habitats. Additionally, removal of hardwood trees may increase the breeding season habitat quality for paper wasps that hunt and nest in areas that are more open, while simultaneously limiting potential winter hibernacula habitat, typically found in mature hardwood tree cavities for Red-cockaded Woodpeckers. Common cavity management and translocation techniques may need to be altered to mitigate greater paper wasp and mud dauber activity at Red-cockaded Woodpecker cavity inserts in Pinus serotina (Pond Pine) pocosin habitat. We suggest using graduated rubber stoppers rather than screens that fail to exclude insect taxa or conducting translocations prior to the formation of winter aggregations of paper wasps.

Dendroecological investigation of red-cockaded woodpecker cavity tree selection in endangered longleaf pine forests

Old-growth longleaf pine (Pinus palustris) is a keystone/foundation species for 29 threatened or endangered species in the Coastal Plain of the southeastern United States. The endangered red-cockaded woodpecker (Dryobates borealis; RCW) and endangered longleaf pine have an established ecological association. Here, we explore differences in climate/growth response and radial growth disturbance events in trees with RCW cavities compared to non-cavity trees in the Sandhills Gameland Reserve in North Carolina, USA. Using standard dendrochronological techniques, we collected and analyzed core samples from trees selected by RCW for their cavities (RCWC) and adjacent control trees (RCWCo) that had no visible cavity. We developed RCWC and RCWCo tree-ring chronologies that allowed us to examine if climate vulnerability is a component of the RCW selection process for their nests. Specifically, we investigated climate/growth responses, radial growth suppressions, and physical characteristics of both tree types through a comparison of tree age, latewood radial growth measurements, and number of resin ducts. For long-term climate response (1910–2018), we found no significant differences between RCWC and RCWCo trees. However, we identified temporal differences in climate/growth relationships between RCWC and RCWCo as well as significant differences in the number of suppression events and spatially-grouped suppression events. For tree physiology, we found more resin ducts during 1950–2018 in RCWC trees. Our dendroecological-based investigation examines multiple factors in addressing the question of why RCWs select specific longleaf pine trees for cavities, which may help improve conservation efforts for RCW and longleaf pine.

Capsaicin as a Tool for Repelling Southern Flying Squirrels from Red-cockaded Woodpecker Cavities

Capsaicin as a Tool for Repelling Southern Flying Squirrels from Red-cockaded Woodpecker Cavities

Resin Production in Natural and Artificial Red-Cockaded Woodpecker Cavity Trees

Resin flow was measured in red-cockaded woodpecker (Picoides borealis Vieillot) clusters in longleaf pine (Pinus palustris Mill.) in the southern region of the Angelina National Forest, Texas. Resin flow (ml) at 1.4 m height over 24 hrs was measured from one 2.5 cm punch through the phloem between 0700 and 1000 hrs from March 1999 to September 2000, for a total of 9 measurements per tree. Resin was sampled in naturally active cavity trees, artificial (insert) active, natural inactive, artificial inactive and control pines (84 sample trees). Resin flow pattern was significantly different during the year, but not significantly different in the cavity tree type resin flow. Cavity trees in the 90th percentile (>33.0 ml resin in 24 hrs) were defined as super resin producing. High average resin flows in August 1999 and September 2000 indicate when to sample resin for potential cavity trees. Regression equations were produced to estimate future resin production.

A model of gas mixing into single-entrance tree cavities during wildland fires

The level of protection to fauna provided by tree cavities during wildland fires is not well understood. Here we present a model for estimating the transport of combustion gases into cylindrical, single-entrance cavities during exposures caused by different wildland fire scenarios. In these shelters, the entrance occurs near the top of the cavity. This empirical model was developed from a suite of numerical experiments using the National Institute of Standards and Technology’s Fire Dynamics Simulator, which spanned a range of entrance diameters, wind speeds, gas temperatures, and vertical angles of incidence. To evaluate the model’s predictions, it was used to replicate, with great accuracy, a time series of carbon monoxide (CO) concentrations in a controlled experiment where a fabricated cylindrical cavity was exposed to combustion products. The time constant for cavity filling is proportional to the ratio of cavity volume to entrance area. Hot gases lead to significant stratification within the cavity during exposures. To demonstrate the model’s potential use in predicting faunal exposures in the context of land management, we show that the model can be used to estimate dosage within red-cockaded woodpecker (Picoides borealis Vieillot, 1809) cavities without requiring temporally detailed, local measurements of wind speed and combustion product concentrations.

Resin-Barrier Maintenance as a Mechanism of Differential Predation Among Occupants of Red-Cockaded Woodpecker Cavities

Abstract. The endangered Red-cockaded Woodpecker (Picoides borealis) is a cavity-limited cooperative breeder that excavates cavities in living pines and maintains a resin barrier that repels rat snakes (Elaphe obsoleta and E. guttata), its principal predators. Heterospecific occupants of Red-cockaded Woodpecker cavities (cavity kleptoparasites) exacerbate the limitation of cavities. However, heterospecifics do not maintain the resin barrier, which deteriorates without upkeep. Thus, we predicted that heterospecific occupants of Red-cockaded Woodpecker cavities should suffer rates of nest predation higher than the Red-cockaded Woodpecker's. We compared the daily nest-survival rates of the Red-cockaded Woodpecker and two heterospecific occupants of its cavities, the Red-bellied Woodpecker (Melanerpes carolinus) and Great Crested Flycatcher (Myiarchus crinitus), in two forests in northern Florida. Results from both forests supported the differential-predation hypothesis. Although during incubation the three s...

Kleptoparasitism of a Red-Cockaded Woodpecker (Picoides borealis) Nest Cavity by a Red-Bellied Woodpecker (Melanerpes carolinus)

Abstract We report the kleptoparasitism of a Picoides borealis (Red-cockaded Woodpecker) cavity by a Melanerpes carolinus (Red-bellied Woodpecker). We believe this is the first video documenting kleptoparasitism of a Red-cockaded Woodpecker nest by a male Red-bellied Woodpecker in which both a nestling and an attending adult Red-cockaded Woodpecker adult were forcibly ejected. The Red-bellied Woodpecker was resolute in its attempt to usurp the nest, reaching into the cavity over 2000 times in an attempt to evict the cavity occupants. The male Red-bellied Woodpecker and his mate took over the cavity soon after. Adult Red-cockaded Woodpeckers continued to visit their nest cavity during diurnal hours for 2 days post-kleptoparasitism. It is important that resource managers incorporate proactive management techniques to lessen the impact of interspecific competition for cavities, especially in smaller or fragmented Red-cockaded Woodpecker populations.

Scent deterrence to reduce southern flying squirrel kleptoparasitism of red-cockaded woodpecker cavities

When establishing new populations of endangered red-cockaded woodpeckers (RCW; Picoides borealis), cavity kleptoparasites can pose a considerable obstacle to successful restoration. Southern fl ying squirrels (SFS; Glaucomys volans) are the principal kleptoparasite of RCW roost and nest cavities. Managers restoring RCW populations primarily use labor-intensive, direct removal to mitigate cavity competition by SFS. We fi eld tested the use of red fox (Vulpes vulpes) urine and rat snake (Elaphe spp.) musk as predator scents to examine if SFS could be deterred from using RCW cavities and to observe RCW roost behavior at cavities treated with red fox urine. Scent deterrence proved ineffective in preventing SFS use of RCW cavities, while RCWs showed no behavioral response to scent treatment. Managers should continue using squirrel excluder devices, and direct removal to mitigate SFS kleptoparasitism of RCW cavities when restoring critically endangered populations.

Texas Ratsnake Predation on Southern Flying Squirrels in Red-Cockaded Woodpecker Cavities

Texas Ratsnake Predation on Southern Flying Squirrels in Red-Cockaded Woodpecker Cavities

Texas Ratsnake Predation on Southern Flying Squirrels in Red-Cockaded Woodpecker Cavities

Elaphe spp. (ratsnakes) are frequent predators on cavity-nesting birds and other vertebrates, including Glaucomys volons (Southern Flying Squirrels). They are known predators of Picoides borealis (Red-cockaded Woodpeckers), especially during the nestling phase. Picoides borealis cavities are frequently occupied by Southern Flying Squirrels, often several squirrels per cavity. Behavioral aspects of ratsnake predation on flying squirrels in woodpecker cavities is an important component required for a full understanding of the potentially complex interaction between Red-cockaded Woodpeckers, Southern Flying Squirrels, and ratsnakes. We induced previously captured Elaphe obsoleta (Texas Ratsnake) to climb boles of pine trees and gain access to Red-cockaded Woodpecker cavities known to contain Southern Flying Squirrels, and observed the resulting predatory interactions. Eight of nine ratsnakes successfully captured 14 of 22 Southern Flying Squirrels present in the cavities.

Do Abandoned Woodpecker Cavities Provide Secondary Cavity Nesters Protection from Climbing Snakes?

Abstract The pine forests of the southeastern United States support a number of cavity-nesting birds as well as several species of rat snakes (Pantherophis spp.). Rat snakes are well-documented nest predators, and nest predation of some of the region's cavity nesters is higher than in other areas. Picoides borealis (Red-cockaded Woodpeckers) and Melanerpes eyrthrocephlus (Red-headed Woodpeckers) invest substantial energy in excavating nest and roost cavities in particular trees, presumably to reduce snake predation. The abandoned cavities of these woodpeckers are important nest sites for many other cavity nesters and may provide protection from snakes. I examined the climbing ability of P. guttata (Red Cornsnake) on abandoned Red-cockaded Woodpecker cavity trees and on barkless snags similar to those used by Red-headed Woodpeckers for nest cavities. Compared to snakes climbing on control trees, snakes (n = 9) either took longer to climb to abandoned Red-cockaded Woodpecker cavities, or where unable to cli...

EVIDENCE OF POSITIVE INDIRECT EFFECTS WITHIN A COMMUNITY OF CAVITY-NESTING VERTEBRATES

Abstract In a community of ≥3 competing species, one species may also have a positive indirect effect on another by suppressing a third, shared competitor. We examine the potential for similar interactions among Red-cockaded Woodpeckers (Picoides borealis) and two of its cavity kleptoparasites: southern flying squirrels (Glaucomys volans) and Red-bellied Woodpeckers (Melanerpes carolinus). We hypothesized that flying squirrels have a positive indirect effect on Red-cockaded Woodpeckers by suppressing Red-bellied Woodpeckers. We monitored occupancy of Red-cockaded Woodpecker cavities on 16 territories for one year, and then regularly removed flying squirrels from Red-cockaded Woodpecker cavities for one year on eight territories, each paired with a control. We predicted that flying squirrel removal would competitively release Red-bellied Woodpeckers, which in turn would preempt a positive occupancy response by Red-cockaded Woodpeckers. During the removal phase, flying squirrel occupancy decreased 53% on th...

CAVITY-NEST WEBS IN A LONGLEAF PINE ECOSYSTEM

Abstract Cavity-nesting communities can be viewed as interconnected webs that interact through the creation of and competition for cavities as nest sites. Using a web approach, we depicted the flow of cavity creation and use in the cavity-nesting bird community of a Florida longleaf pine (Pinus palustris) ecosystem to examine the relationship between cavity-nesting bird abundance and cavity resources, and to identify species with potential to respond to cavity management for the endangered Red-cockaded Woodpecker (Picoides borealis). We identified two groups into which most cavity-nesting species could be placed: 1) six species associated with pine snags and Red-cockaded Woodpecker cavities, and 2) five species associated with hardwood snags. We found the majority of nests (60%) in large pine snags. Red-cockaded Woodpeckers and Northern Flickers (Colaptes auratus) excavated most cavities used by other cavity nesting birds. The Northern Flicker was the primary creator of large nest cavities, through its ex...

Protecting Red-Cockaded Woodpecker Cavity Trees Predisposed to Fire-Induced Mortality

Abstract Reducing fire-induced mortality of cavity trees used by red-cockaded woodpeckers (Picoides borealis) is a challenge and concern in managing this federally endangered species. Prior to the 2001 burning season, 814 active and inactive longleaf pine (Pinus palustris) cavity trees on Eglin Air Force Base (AFB) in northwest Florida, USA, were prepared via 6 protection methods (combinations of mechanical, hand, and backfiring preparation) and monitored for postburn survival after 1 year. We collected data on a suite of variables that may be useful in determining cavity tree predisposition to fire-induced mortality. Mortality of protected trees (2.62%) was significantly lower than that of unprotected trees (6.18%), and protection methods did not differ in their effectiveness at preventing mortality. Bark char was significantly more prevalent on unprepared control trees than protected trees, but no differences were apparent among protection treatments. Mechanical clearing alone took the least amount of t...

Role of Predator Odor in Roost Site Selection of Southern Flying Squirrels

Roost site selection should be influenced, in part, by predator avoidance strategies. Prey species may use olfactory cues to assess predation risk. Our objective was to determine if southern flying squirrels (Glaucomys volans) use olfaction for assessing predation risk and selecting safe roosting sites. We tested the response of captive flying squirrels to several scents placed inside nest boxes. Squirrels spent significantly less time overnight in nest boxes scented with fox squirrel (Sciurus niger) fur, bobcat (Lynx rufus) fur, red fox (Vulpes vulpes) urine, raccoon (Procyon lotor) fur, king snake (Lampropeltis getula), and corn snake (Elaphe guttata) than unscented (control) boxes. Nest boxes with gray squirrel (S. carolinensis) fur, red fox urine, raccoon fur, and corn snake scent were selected as daytime roosting sites less than would be expected by chance. Southern flying squirrels are a major usurper of red-cockaded woodpecker (Picoides borealis) cavities and may reduce reproduction in this endangered bird. Our results indicate that predator odor may be an effective means of deterring flying squirrels from roost sites. If so, predator scent application could be utilized to reduce negative impacts of flying squirrels on red-cockaded woodpeckers.

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...

Differential Estimates of Southern Flying Squirrel (Glaucomys volans) Population Structure Based on Capture Method

It is commonly assumed that population estimates derived from trapping small mammals are accurate and unbiased or that estimates derived from different capture methods are comparable. We captured southern flying squirrels (Glaucomys volans) using two methods to study their effect on red-cockaded woodpecker (Picoides borealis) reproductive success. Southern flying squirrels were captured at and removed from 30 red-cockaded woodpecker cluster sites during March to July 1994 and 1995 using Sherman traps placed in a grid encompassing a red-cockaded woodpecker nest tree and by hand from red-cockaded woodpecker cavities. Totals of 195 (1994) and 190 (1995) red-cockaded woodpecker cavities were examined at least three times each year. Trappability of southern flying squirrels in Sherman traps was significantly greater in 1995 (1.18%; 22,384 trap nights) than in 1994 (0.42%; 20,384 trap nights), and capture rate of southern flying squirrels in cavities was significantly greater in 1994 (22.7%; 502 cavity inspections) than in 1995 (10.8%; 555 cavity inspections). However, more southern flying squirrels were captured per cavity inspection than per Sherman trap night in both years. Male southern flying squirrels were more likely to be captured from cavities than in Sherman traps in 1994, but not in 1995. Both male and female juveniles were more likely to be captured in cavities than in traps in both years. In 1994 males in reproductive condition were more likely to be captured in cavities than in traps and in 1995 we captured significantly more reproductive females in cavities than in traps. Our data suggest that population estimates based solely on one trapping method may not represent true population size or structure of southern flying squirrels.

The longevity of large pine snags in eastern Texas

Habitat for cavity-nesting wildlife is closely tied to the availability of standing dead trees (snags). Large snags (>40 cm dbh) are particularly important because they provide cavity-excavation substrate for both large and small cavity excavators. Historically in the southern United States, common belief has been that the utility of pine (Pinus spp.) snags for cavity nesters occurs for only a short period of time after tree death because pine snags quickly decay and fall to the ground. We studied the deterioration rate and ultimate falling of large pine snags in eastern Texas over a 20-year period (1983–2003). Coinciding with our annual checks of red-cockaded woodpecker (Picoides borealis) cavity-tree clusters, we checked the status and height of all red-cockaded woodpecker cavity trees that died. We determined the cause of death and tree species of 136 cavity tree snags (=25.4 m at death) and monitored their height annually until they were <1 m in height. Five years after tree death, 92 snags (67.6%) were still standing and averaged 13.9 m in height. Ten years after tree death, 21 snags (15.4%) were still standing and averaged 10.0 m in height. After 15 years 4 snags (2.9%) averaging 5.3 m in height still remained standing. Two snags (1.5%), averaging 2.7 m in height, survived through 19 years but had fallen by the end of the twentieth year. Pines dying from wind snap at mid-bole survived longer as snags (=9.7 years) than pines killed by bark-beetles (Dendroctonus spp.) (=5.9 years). Longleaf pine (Pinus palustris) snags remained standing longer (=8.0 years) than loblolly pine (P. taeda) snags (=6.0 years) (P < 0.05), but not longer (P>0.05) than shortleaf pine (P. echinata) snags (=6.6 years).