Protected Species in Pennsylvania: Blackpoll Warbler

Introduction

Migratory songbirds are important to many recreationalists who look for them at expected times of the year. Although many people enjoy seeing the beautiful plumages and listening to bird songs, most do not realize that some species have been facing growing difficulties across their ranges. The Blackpoll Warbler (Setophaga striata) is a species currently considered endangered in Pennsylvania. The population has been observed breeding in Pennsylvania for only 15 years. It is not necessarily declining in Pennsylvania, but since there are only a handful of other breeding locations in the Northeast, Pennsylvania is still considered important for protecting this species in the long term.

Background 

The Blackpoll warbler is a relatively small songbird belonging to Parulidae, or the family of birds known as the new-world warblers or wood-warblers. This species primarily inhabits boreal forests across North America and especially in Northern Canada during the breeding season, migrating south to Venezuela and the bordering portions of adjacent nations during the winter. This journey is one of the longest migration routes of any other songbird species and is so intense that Blackpoll Warblers must double their body weight in order to survive the flight.

The breeding range of Blackpoll Warblers in Pennsylvania is limited mostly to forests in the northern part of the state where they have also been found inhabiting spruce and hemlock (Tsuga spp.) forests. Many more Blackpoll warblers can be found throughout the state for short periods of time during migration, but these birds largely breed in Canada and New England and so are not considered part of the Pennsylvania population.

Their preferred habitats are found in boreal forests, or ecosystems dominated by coniferous species such as pines, spruces, and firs. However, their favorite habitats consist mostly of black spruce which occur in high abundance in Northcentral Canada but also in some parts of Pennsylvania. Blackpoll warbler nests can be found low in the tree, no more than 30 feet up. They are built by the female, are made of twigs, bark, grass, moss, and lichens, and are considered bulky and open structures. Blackpoll warblers are opportunistic feeders but will mainly prey upon commonly found insects including aphids, scales, caterpillars, beetles, gnats, sawflies, wasps, and ants to name a few. They prefer to occupy areas with a medium density underbrush located near bodies of water where most insects propagate.

Causes of Decline

Timbering in the 1800s-1900s in the northeastern US contributed greatly to the decline of this species. The Blackpoll Warbler has now been listed as endangered within Pennsylvania for over a decade. Although global populations of this bird have been relatively stable, Blackpoll Warbler populations in PA still struggle to expand. Threats to the species today include habitat destruction or infringement on habitat by humans.

Species Conservation Activities

There is no species recovery plan in place for Blackpoll warblers in Pennsylvania and it is not listed on the Pennsylvania Wildlife Action Plan for 2015-2025. It is unclear why Blackpoll warblers were not included, but since the species was never found in high abundance in Pennsylvania historically, "recovery" may not be the appropriate strategy to apply to this population. Instead, the conservation actions taken by the state appear to be helping with habitat/population expansion and protection to help avoid declines in the future. For example, the PA Game Commission does list Blackpoll warblers under chapter 133, subchapters A & B of the PA Game and Wildlife Code, which protects a number of non-game bird species and classifies them as either threatened or endangered. The Game Commission has also placed nesting sites of the Blackpoll warbler under 'Important Bird Area' status, which are often off-limits to the public. Many of these nesting sites are on protected in state game lands, with the highest number of nesting sites occurring on SGL 57 around Tamarack Swamp.

Other Recommendations for Species Protection

With no recovery plan in place, and fairly minimal protection and expansion efforts, public and landowner education will be an important tool for raising awareness and supporting species expansion. People who like to watch birds in nature will often hike off trails to try and get as close to the birds as possible for better viewing. Blackpoll Warblers prefer to nest relatively low to the ground and use the brushy understory to forage, so this activity can have a negative impact on important habitat, as well as the bird’s sense of security.  Anyone trying to spot these birds should be respectful and try to leave as little impact on the environment as possible.

Pennsylvania is dominated by private forest lands, so landowners also need to know about how to best protect Blackpoll Warblers on their land. Forest management helps keep forests healthy and resilient. Because some management activities can be cost-prohibitive, owners sometimes require assistance in reaching their management goals. The Pennsylvania Department of Conservation and Natural Resources has service foresters available in every county to help landowners develop a management plan that helps protect important bird species. Since many forest owners are also interested in harvesting timber at some point, it may be useful for logging crews and forestry professionals to also be aware of this species. Logging crews working in conifer forests may encounter these birds or even destroy their habitat without realizing it. Loggers who do notice this species on a job site should notify the Department of Conservation of Natural Resources (DCNR) or the Pennsylvania Game Commission (PGC). These two agencies are well equipped to recommend a best course of action to protect this species, while still getting work done. If you contact the DCNR they will most likely tell a logging crew to avoid cutting any pine thickets with high abundances of Red or Black Pine. It is especially important to avoid harvesting any young to mid-aged trees of medium heights surrounding any of these pine thickets as these are often used by Blackpoll Warblers for hunting and foraging purposes.

Student Authors

This article was written in coordination with undergraduate students as part of a class project at Pennsylvania State University.

References

Claire A. Runge, James E. M. Watson, Stuart H. M. Butchart, Jeffrey O. Hanson, Hugh P. Possingham, & Richard A. Fuller. (2015). Protected areas and global conservation of migratory birds.

Covino, Kristen M. (2020) "Spring migration of blackpoll warblers across North America." Avian Conservation and Ecology.

Gross, Doug. "Blackpoll Warbler." Pennsylvania Game Commission, Commonwealth of Pennsylvania, 19 Aug. 2014.

"Blackpoll Warbler." Audubon, 4 Nov. 2019.

Gross, D. A. (2010). Pennsylvania boreal conifer forests and their bird communities: past, present, and potential. In In: Rentch, James S.; Schuler, Thomas M., eds. 2010. Proceedings from the conference on the ecology and management of high-elevation forests in the central and southern Appalachian Mountains. 2009 May 14-15; Slatyfork, WV. Gen. Tech. Rep. NRS-P-64. Newtown Square, PA: US Department of Agriculture, Forest Service, Northern Research Station: 48-73. (pp. 48-73).

Zawatski, E. J., Gross, D. A., & Brittingham, M. C. (2019). Habitat of breeding blackpoll warblers at a persistent extralimital breeding site in pennsylvania. Northeastern Naturalist, 26(1), 31-42.