The Eastern Towhee is a large sparrow found in eastern North America. This striking bird with rufous sides and a black hood is common in many areas but rare in parts of the Northeast and northern Midwest. Understanding the abundance and distribution of the Eastern Towhee can help us appreciate the diversity of bird life across different regions.
What is the Eastern Towhee?
The Eastern Towhee (Pipilo erythrophthalmus) is a large, striking sparrow that breeds in eastern North America. Some key facts about this species:
- It belongs to the bird family Emberizidae, which includes sparrows, juncos, cardinals, and buntings.
- Adults have rufous sides, white bellies, and black heads, backs, wings, and tails with white spots.
- They get their name from their loud “towhee” or “drink-your-tea” call.
- They breed in thickets, forest edges, regrown clearcuts, and brushy areas across eastern North America.
- Their diet consists mainly of seeds and insects which they scratch out from leaf litter on the forest floor.
- They build nests low in bushes or vine tangles, laying 3-5 eggs.
The Eastern Towhee was once considered a single species with the Spotted Towhee of western North America. But differences in appearance, voice, habitat, and genetics led to the two being classified as distinct species in 1995. The Eastern Towhee remains common over much of its breeding range of eastern North America.
Eastern Towhee Abundance and Population
According to the North American Breeding Bird Survey, Eastern Towhees number approximately 13 million breeding adults across their range. Their total global population is estimated at 25 million individuals.
This makes the Eastern Towhee a fairly common bird over much of its range. However, its abundance varies greatly across different regions, states, and habitats.
Some key facts about Eastern Towhee abundance:
- They are most abundant in the southeastern United States and along the East Coast up through New England.
- They are common and increasing across the Appalachians and interior eastern forests.
- They are rare and localized in northern parts of the Midwest such as Minnesota and Wisconsin.
- They are nearly absent across the Great Plains and western North America.
So while Eastern Towhees are numerous in woodlands and thickets of the eastern U.S., their numbers drop off in the northern and western parts of their range. Several factors likely contribute to their scarcity in these regions, which we’ll examine next.
Range and Distribution
Eastern Towhees breed across eastern North America from southeastern Canada through the eastern United States. Their breeding range extends west to Minnesota, Iowa, Missouri, Arkansas, and Louisiana.
Here is a map showing the breeding range of the Eastern Towhee:
Within this broad range, Eastern Towhees breed most densely in the southeastern states from Texas to Florida to Virginia. Abundance declines towards the northern and western edges of the range in areas like Minnesota, Wisconsin, Michigan, and Ontario.
The map shows isolated, localized breeding populations in states like Wisconsin, Minnesota, and Michigan. These outlying populations are rare and scattered compared to areas farther south and east.
So while Eastern Towhees occupy a wide range overall, their distribution is irregular, with greater concentrations in southeastern states. Their range also overlaps and intergrades with the Spotted Towhee in the Great Plains, causing confusion in identification and recording in that region.
Habitat Preferences
The abundance of Eastern Towhees depends largely on the availability of suitable breeding habitat. This species prefers habitats with dense undergrowth and thick ground cover.
Some of the key habitats used by breeding Eastern Towhees include:
- Shrublands and regenerating clearcuts
- Forest edges and openings
- Overgrown fields and power line corridors
- Pine-oak associations and dry upland forests
- Brushy, shrubby areas near streams and swamps
Territory sizes range from 0.25-4 acres but average around 1.25 acres. Optimal habitat provides a dense leaf litter layer along with good cover within 1-3 feet off the ground for nesting and foraging.
The table below summarizes the typical vegetation density and structure preferred by breeding Eastern Towhees:
Vegetation Layer | Optimal Density/Height |
---|---|
Canopy | Open to partially open |
Understory | Dense thickets 1-10 ft high |
Ground cover | Abundant leaf litter with bare ground |
The availability of these scrubby, brushy habitats with dense undergrowth declines towards the western edge of the Eastern Towhee’s range. The scarcity of ideal habitat likely contributes to their rarity in areas like Minnesota and Wisconsin compared to farther south and east.
Sensitivity to Habitat Fragmentation
Research shows that Eastern Towhees are sensitive to habitat fragmentation and the breaking up of large forest tracts. Fragmentation opens up the interior forest and creates more edge habitat.
Eastern Towhees favor brushy habitat along forest edges. However, studies have found they are still vulnerable to fragmentation and declines in large forest patch size for a few key reasons:
- Nest predation and brood parasitism increases near forest edges.
- Their preferred shrubby habitat is transient and declines over time in fragmented areas.
- Fragmentation creates habitat for competitors like Common Grackles which may displace towhees.
- Towhees have weak dispersal abilities across open habitats between fragments.
So while towhees initially occupy regrowth areas near edges, fragmentation still degrades their breeding habitat over time. This likely contributes to their scarcity in parts of the highly fragmented Midwest.
Threats and Conservation Status
Currently, Eastern Towhees are considered a species of Least Concern by the IUCN Red List due to their large range and population size. However, they do face threats from habitat loss and degradation in parts of their range.
Some key threats and conservation issues include:
- Habitat loss to development and agriculture, especially in Southeastern states
- Invasive shrubs crowding out native vegetation in some areas
- Excessive deer browsing altering understory growth
- Climate change shifting habitat suitability northwards
Conservation measures for Eastern Towhees include protecting large tracts of mature forest with natural disturbance regimes. Allowing clearcuts and agricultural fields to regenerate into shrubby habitat also benefits towhees. Removal of invasive species and monitoring deer impacts may also be needed in some regions.
Causes of Rarity in the Northern Edge of Range
We’ve covered several factors already that help explain why Eastern Towhees are rare and localized in the northern Midwest states such as Minnesota and Wisconsin:
- These areas mark the northwestern limit of the towhees’ breeding range.
- Ideal scrubby, shrubby habitat is less available in these cooler climates.
- High fragmentation of forests decreases habitat suitability.
- Towhees have weak dispersal across open habitats between fragments.
- There may be increased competition from northern species like Common Grackles.
In addition, northern populations likely experience higher overwinter mortality. Eastern Towhees migrate south to the Southeastern U.S. and Mexico for winter. The journey is longer and more perilous for northern fringe populations. Higher mortality on migration helps keep northern populations small.
The infrequency of breeding records from states like Wisconsin and Minnesota reflect that towhees are a locally distributed, uncommon species in these areas. Abundance increases southwards where habitat is more suitable.
Rarity in Specific States
We can look more specifically at Eastern Towhee abundance and trends in a couple of states where they are rare:
Wisconsin
Eastern Towhees are considered an uncommon breeder in Wisconsin. Breeding Bird Survey data indicates they are found locally in the southern third of the state, with possibly only a few hundred pairs statewide. The state DNR classifies Eastern Towhees as a species of Special Concern due to its scattered distribution, specific habitat needs, and vulnerability to climate change. Habitat loss and fragmentation have decreased suitable habitat over time. Towhees also face increased competition as shrubland habitats mature. Continued habitat management and conservation will be important for sustaining this rare breeding species in Wisconsin.
Minnesota
The Eastern Towhee is listed as a Species of Special Concern in Minnesota. The state DNR says its breeding range is limited to the southeastern corner of the state with isolated records elsewhere. Breeding Bird Surveys between 1966-2015 indicate a 4.1% annual decline in Minnesota’s towhee population. However, the data has a high margin of error due to small sample sizes where they breed. Minnesota represents the northwestern fringe of the towhee’s range where scrubby habitat is scarce and fragmentation prevalent. Targeted conservation of regenerating wooded areas will be important for maintaining towhee populations in the state.
How Does This Compare to Spotted Towhee?
The Eastern Towhee’s scarcity in the northern Midwest contrasts sharply with its western counterpart, the Spotted Towhee. Spotted Towhees are common across much of the western United States and inland west of the Great Plains.
Some key differences:
- Spotted Towhees have a much broader range extending across western North America.
- They occupy diverse habitats from riparian areas to forest edges to snowmelt meadows.
- They are common and increasing across many western states and provinces.
- They have a larger estimated global population of 32 million.
- They are still widespread and abundant on the northern and western fringe of their range.
So while the Eastern Towhee becomes increasingly rare toward the north and west, the Spotted Towhee remains widespread across much of western North America. Its adaptability to varied habitats and environments makes it much more common within its range compared to the Eastern Towhee.
Summary and Conclusions
- The Eastern Towhee is a fairly common breeding bird across the southeastern United States.
- Abundance declines toward the north and west within its breeding range.
- The species is rare and localized in parts of the upper Midwest such as Wisconsin and Minnesota.
- Scarcity in these areas is due to limited habitat, sensitivity to fragmentation, longer migrations, and other factors.
- Conserving large tracts of brushy habitat will benefit Towhees in the northern parts of their range.
- The Eastern Towhee exhibits a patchy, irregular distribution compared to the widespread Spotted Towhee of western North America.
In conclusion, the Eastern Towhee occupies a broad range across eastern North America, but shows irregular abundance patterns within that range. While common in the Southeast, its rarity increases toward the northern limits in states like Wisconsin and Minnesota. Maintaining habitat connectivity and mitigating fragmentation will be important for conserving Towhee populations in these areas. Careful monitoring and management of this species will be needed, especially as climate change alters the landscapes this selective bird inhabits.