Red bellied woodpeckers are a medium-sized woodpecker species native to eastern North America. Their range extends from southern Florida up through Maine. While fairly common through most of their range, red bellied woodpeckers are less frequently encountered in the northernmost parts of their range, including Maine. This has led some to believe that red bellied woodpeckers are rare in Maine, but the true situation is more nuanced. In this article, we will explore the distribution and abundance of red bellied woodpeckers in Maine and discuss factors that may contribute to them being less frequently observed in parts of the state.
Range and Habitat of Red Bellied Woodpeckers
The red bellied woodpecker is found across the eastern half of the United States, ranging from southern Florida to southeastern South Dakota in the west and north up through southern Ontario, Quebec, New Brunswick, and Maine. Their range centers on the southeastern United States but extends up the Atlantic coast and along major river systems like the Ohio and Mississippi.
Red bellied woodpeckers inhabit open forests, especially those containing mature trees. They frequent deciduous forests, river bottoms, swamps, orchards, parks, and residential areas with large trees. Their ideal habitat contains large dead trees (snags) for nesting and roosting along with a brushy understory for foraging on seeds, fruits, and arthropods.
In Maine, red bellied woodpeckers can be found statewide but are most abundant in southern and coastal regions. The southern part of the state falls within the core part of their range where habitat is optimal. Moving north, their numbers gradually thin out. However, red bellies occur locally up to the northernmost parts of Maine, just reaching the Canadian border.
Abundance in Southern and Coastal Maine
Red bellied woodpeckers are a relatively common sight in southern Maine, which is characterized by a mix of oak-hickory forests, pine barrens, old fields, swamps, and suburban neighborhoods. Mature forests with snags and a brushy understory provide excellent habitat. Backyard bird feeding has also benefited red bellied woodpeckers, providing supplemental food during winter.
Along the coast, red bellied woodpeckers frequent deciduous forests as well as residential areas. Coastal pine barrens also provide suitable habitat. Acorns from oak trees and fruits from shadbush, dogwood, sumac, and other understory trees and shrubs help sustain red bellied woodpeckers in coastal regions.
Breeding Bird Survey data shows the highest densities of red bellied woodpeckers in southern and coastal counties like York, Cumberland, Sagadahoc, Lincoln, and Knox Counties. They are a relatively common year-round resident throughout these regions.
Declining Abundance Further North
As one moves further north in Maine, red bellied woodpeckers occur at lower densities and their range becomes more patchy and localized. Most observations come from river valleys and urban areas with mature trees, rather than extensive forested areas.
Counties along Maine’s northern border generally have far fewer red bellied woodpecker reports compared to southern counties. Aroostook, Somerset, Piscataquis, and Franklin Counties are less frequented by red bellies. The harsh winters and different forest composition (more conifers) in this boreal zone are less suitable habitat.
There are certainly resident red bellied woodpeckers that tough out the winters in northern Maine. But their numbers are lower here than further south, and they tend to occur only locally in pockets of appropriate habitat. For example, riparian woodlands along the Aroostook River provide habitat for red bellies in Aroostook County.
Factors Affecting Distribution in Maine
What factors may be responsible for the declining numbers and localized distribution of red bellied woodpeckers in northern Maine? A few hypotheses help explain this trend:
Climate
The colder winters and shorter growing seasons present a climate challenge for red bellied woodpeckers trying to inhabit northern Maine. They evolved in the temperate southeastern U.S. and may be limited by the subarctic conditions towards the Canadian border. The severity of winter may limit their ability to find sufficient food.
Forest Composition
Maine’s forest transitions from deciduous and mixed forests in the south to boreal coniferous forests in the north. This habitat favors birds like black-backed woodpeckers while red bellied woodpeckers prefer mature hardwoods. There are simply fewer large mast-producing trees like oaks and beeches that red bellies depend on in northern Maine.
Nested Range Limit
Northern Maine represents the extreme northern limit of the red bellied woodpecker’s range. Populations tend to thin out and become patchy at the fringes of a species’ range. Maine is no exception, with the Canadian border approximating the northernmost extent these woodpeckers can survive the winter.
Observer Bias
There are fewer birders and nesting reports coming from Maine’s vast northern forests compared to southern regions closer to cities like Portland and Bangor. This may skew perception of red bellied woodpecker abundance. Their presence in remote northern areas is likely underreported.
Seasonal Changes in Abundance
In addition to the south-to-north gradient in abundance across Maine, red bellied woodpeckers also demonstrate seasonal changes in abundance:
Breeding Season
Red bellied woodpeckers are most abundant and conspicuous during the breeding season from April to July. Their loud territorial drumming and vocalizations make them more noticeable. Nest building and feeding of young also necessitate increased foraging.
Winter Movements
Some southward movement out of the far northern parts of their range may occur in winter as food becomes scarce. This would result in lower winter numbers in northern Maine. However, red bellies seem to be mostly permanent residents throughout their range.
Irruptive Years
In some years, red bellied woodpecker numbers appear to suddenly increase in parts of northern Maine. This may represent irruptive movement of southern birds outside their normal range triggered by food shortages. Their abundance quickly returns to normal after these irregular irruptions.
Threats and Conservation
Although red bellied woodpeckers remain common over most of their range, they do face threats in some areas:
Habitat Loss
Conversion of mature forests to development or young second growth stands reduces the availability of nesting cavities and mast-producing trees. This has impacted populations locally.
Competition
The northern flicker is another woodpecker expanding its range eastward into New England. Where their ranges overlap, flickers may compete with red bellies for food and cavities.
Climate Change
Warmer winters may allow red bellies to expand northward in the Northeast. But climate change also threatens their food sources like oak forests and southern pine forests. The long term impacts are uncertain.
Conservation Efforts
Protecting mature forests and dead snags helps provide habitat across their range. Leaving dead trees and planting oaks and beechnut trees also benefits red bellied woodpeckers. Monitoring their northern range limits in Maine will reveal if climate change enables expansion.
Conclusions
In conclusion, red bellied woodpeckers are resident throughout Maine but decrease in abundance moving northward. They reach the northern limits of their range along the Canadian border region. Deep snow, severe winters, boreal forests, and decreasing habitat quality appear to limit their numbers in Maine’s northernmost counties. However, red bellies can be locally common in pockets of suitable habitat like riparian woodlands. More research is needed to clarify winter movements and the irruptive behavior of red bellied woodpeckers in northern Maine. Ongoing monitoring will determine if their range expands over time. Protecting mature hardwood forests will benefit red bellied woodpeckers across their range.