This small 3.8-acre urban woodland fragment in Fort Circle Park supports a surprisingly diverse array of wildlife. Over the course of the two-month study period, we documented a total of 39 vertebrate species, including 8 mammal species and 31 bird species. This diversity shows the importance of preserving and maintaining similar urban forest patches as refuges for wildlife in city environments. The findings also highlight the need to create and protect low-stress corridors that animals can traverse safely in urban landscapes. These corridors allow wildlife to move between green spaces with minimal exposure to urban stressors such as traffic, noise, and artificial lighting. By establishing and maintaining these safe passages, we can facilitate essential animal movements for foraging, breeding, and dispersal, thereby supporting more robust and resilient urban ecosystems.

Our observations revealed a complex ecosystem where native wildlife coexists with and adapts to urban pressures. The presence of several species listed in the DC State Wildlife Action Plan as Species of Greatest Conservation Need, including the Eastern Chipmunk, Virginia Opossum, Brown Thrasher, and Eastern Towhee, and one species listed on the IUCN Red List, the Chimney Swift, highlights the conservation value of this small woodland. Moreover, the consistent presence of various species throughout the study period suggests that the site serves as a permanent habitat rather than merely a transitory corridor. The frequent observations of parents and juvenile animals, particularly among raccoons, further emphasize the woodland's role as a functional habitat supporting full life cycles of urban-adapted wildlife.

Over the course of the study, 1,216 individual animals were observed on the camera traps, and 1,446 avian detections were made using bioacoustic recordings. An average of 20 animals were observed per day on camera. 

See a full log of all species detected and observation method in the Appendix

Count: Total number of individuals of all species observed on camera
Occurrences: Total number of observations, regardless of the number of individuals present

A total of 8 mammal species were observed during the study period. The most frequently detected species was the Raccoon (Procyon lotor), with 271 separate detections, of 662 individuals (average of 2.44 individuals per detection). Multiple family units of raccoons were observed on a daily basis, typically consisting of one adult female and 2-4 juveniles. Two distinct family groups were regularly identified, with occasional sightings of solitary adults. Other commonly observed species included Eastern Gray Squirrel (Sciurus carolinensis) with 93 detections and White-tailed Deer (Odocoileus virginianus) with 22 detections.

The majority of mammal activity was nocturnal, with Raccoons, Red Foxes (Vulpes vulpes), and Virginia Opossums being exclusively observed between dusk and dawn. Eastern Gray Squirrels were primarily diurnal, with activity peaking in the morning and late afternoon hours.

Two mammal species observed - the Eastern Chipmunk (Tamias striatus) and Virginia Opossum - are listed as Species of Greatest Conservation Need in the 2015 DC State Wildlife Action Plan.

Below is a list of all 8 mammal species observed during the study period, as well as the count of the total number of individuals observed, and the number of detections. 

Note: A complete log of all individual detections, along with videos and notes, is available in the appendix at the end of this report.

31 bird species were recorded through a combination of camera trap observations and bioacoustic recordings. Based on camera trap data, the most frequently detected species were Gray Catbird (Dumetella carolinensis) with 117 detections and 137 individuals observed, American Robin (Turdus migratorius) with 74 detections and 103 individuals, and American Crow (Corvus brachyrhynchos) with 22 detections and 38 individuals.

Bioacoustic data revealed high activity levels for some species not frequently captured on camera. The most commonly detected species in bioacoustic recordings were Carolina Wren (Thryothorus ludovicianus) with 363 detections and Fish Crow (Corvus ossifragus) with 343 detections. 

Four bird species observed are listed as Species of Greatest Conservation Need in the 2015 DC State Wildlife Action Plan: Brown Thrasher (Toxostoma rufum), Eastern Towhee (Pipilo erythrophthalmus), Chimney Swift (Chaetura pelagica), and Yellow-Billed Cuckoo (Coccyzus americanus). These species, along with several others observed, are facing population declines. Ten species with decreasing populations were observed: Northern Flicker (Colaptes auratus), Eastern Towhee, Brown Thrasher, Chipping Sparrow (Spizella passerina), Chimney Swift, Eastern Wood-Pewee (Contopus virens), Indigo Bunting (Passerina cyanea), Eastern Kingbird (Tyrannus tyrannus), Yellow-Billed Cuckoo, and Killdeer (Charadrius vociferus). Notably, the Chimney Swift was detected seven times in bioacoustic recordings. This species is listed as Vulnerable on the IUCN Red List of Threatened Species, indicating it faces a high risk of extinction in the wild in the medium-term future (20-30 years).

Below is a list of all 31 avian species observed during the study period, as well as the count of the total number of individuals observed, and the number of detections. 

Points of Discussion: 

Fish Crows vs. American Crows. The number of bioacoustic detections of Fish Crows suggest that a significant proportion — perhaps even a majority — of the birds visually identified as American Crows observed on the camera may in fact have been Fish Crows. Their visual similarities being so strong that typically the only way to distinguish them visually is by proximity to water, it was initially assumed that all the crows being seen on the cameras must have been American Crows. The bioacoustic data significantly challenges that assumption, and it is probably a safe bet that many of them were in fact Fish Crows, but it would be impossible to tell for sure one way or the other based purely on the relatively low-resolution videos where they were detected.

American Robin. While American Robin (Turdus migratorius) was the second-most common bird species observed on camera (103 individuals), often with multiple sightings a day, only four American Robins were detected using the bioacoustic data. There are two main possibilities for this discrepancy, neither of which are satisfactory: 1) American Robins vocalize relatively less frequently than many other birds, so they were picked up less by the recording device (this seems unlikely to account for the degree of discrepancy between sightings and acoustic detections); and 2) American Robin vocalizations were miscategorized by the BirdNET system as another species. While spot checks were done on the identified recordings of birds whose calls were well known to the authors, and also comparisons made between the recordings available on trusted sites like Audubon and others, it would be impossible to manually verify all 1,400+ recordings. Of those that were verified, however, they appeared to be highly accurate, and studies indicate accuracy of 70+% for BirdNET, and even higher scores for North American species (see reference in Notes section). It thus remains a mystery as to why so few American robins were detected through bioacoustic recordings. Based on our spot checks of recordings and studies evaluating BirdNET's accuracy, we believe the identifications made were acceptably reliable. Other common city birds like European Starlings and House Sparrows were also not identified through bioacoustics, but over the course of the entire two-month study period not a single one of those two species was seen on any of the four cameras, despite being very common in the urban areas just outside of the woods, so it seems logical that they would also have few (if any) bioacoustic detections. 

 Note: A complete log of all individual detections, along with videos and notes, is available in the appendix at the end of this report. You can also listen to individual bioacoustic recordings — all 1,446 of them — and sort them by species, date and time online at the bioacoustic station website (PUC-5813)

Note: A complete log of all individual detections, along with videos and notes, is available in the appendix at the end of this report.

Note: A complete log of all individual detections is available in the appendix at the end of this report. You can also listen to individual bioacoustic recordings — all 1,446 of them — and sort them by species, date and time online at the bioacoustic station website (PUC-5813)

The urban woodland fragment in Fort Circle Park, despite its modest size, supports several species of conservation concern. These species, identified either through the DC State Wildlife Action Plan (SWAP) as Species of Greatest Conservation Need (SGCN) or listed on the IUCN Red List, underscore the ecological value of this small urban green space.

Among the mammals, two species observed are listed as SGCN: the Virginia Opossum (Didelphis virginiana) and the Eastern Chipmunk (Tamias striatus). While both are considered of Least Concern globally by the IUCN, their inclusion in the DC SWAP highlights their local importance. It's noteworthy that despite their generally stable populations outside urban areas, these species face challenges within the District of Columbia, particularly the threat posed by vehicular traffic, which means their numbers within the city are likely much lower than their potential. This is reflected in our observations, with only one detection each for both the Virginia Opossum and Eastern Chipmunk throughout the study period. These low numbers suggest that while the urban forest fragment provides habitat, additional conservation measures may be necessary to support and increase their populations within the city in the future.

In the avian community, we documented four bird species listed as SGCN: the Brown Thrasher (Toxostoma rufum), Eastern Towhee (Pipilo erythrophthalmus), Chimney Swift (Chaetura pelagica), and Yellow-Billed Cuckoo (Coccyzus americanus). Of particular note is the Chimney Swift, which is not only an SGCN but also listed as Vulnerable on the IUCN Red List. This designation indicates that the Chimney Swift faces a high risk of extinction in the wild in the medium-term future, making its presence in our study area especially significant.

During our study, we observed the presence of domestic animals in the urban woodland fragment, specifically cats (Felis catus) and dogs (Canis familiaris). While these companion animals are an integral part of urban life, their presence in natural areas can have significant ecological impacts, particularly on native wildlife populations.

Of particular concern is the impact of domestic cats on bird populations. Cats, even when well-fed, retain their hunting instincts and can be efficient predators of small birds and mammals. Studies have shown that free-roaming domestic cats can have devastating effects on local bird populations, especially in urban and suburban areas where habitat is already fragmented. The presence of cats in this woodland, even if infrequent, could pose a threat to the diverse bird species we observed, including those of conservation concern. Dogs, while generally less of a direct threat to wildlife, can still cause disturbance through their presence and scent, potentially altering wildlife behavior and habitat use.

Temporal Patterns. The wildlife activity in the urban woodland fragment exhibited distinct temporal patterns throughout the 24-hour cycle. Observations revealed a strong nocturnal bias in animal activity, with nearly three-quarters (73.76%) of all detections occurring during nighttime hours (20:00-07:59). 

Daytime hours (08:00-19:59) accounted for just over a quarter (26.24%) of all wildlife activity, with a relatively even distribution across morning, afternoon, and evening periods. This diurnal activity, while less frequent, still represents significant usage of the habitat by various species. The stark contrast between nighttime and daytime activity levels highlights the diverse temporal niches occupied by different species within this urban woodland, emphasizing the need for round-the-clock habitat protection and management strategies to support the full spectrum of urban wildlife.

3D locator map of the project study woods and surroundings on the DC side of the border