Northern parulas are small wood-warblers that measure 11.4 cm in length and weigh 8.6 g. This species molts twice annually, once before and after the summer breeding season. Both males and females have distinct plumage during the breeding season. During this time, both are blue-gray above with a green, triangular mantle. Tail and wing feathers are a darker shade of blue-gray and they feature a pair of bold, white wing-bars. Both sexes also have bright yellow throats that extend through the breast. The bellies and undertail feathers are unmarked white. The bills are two-toned, with a black upper mandible and a yellow lower mandible that blends with the yellow throat. Breeding males feature distinct white eye-arcs surrounding a black eye stripe that connects to the base of the bill. Breeding males also feature prominent black and rufous breastbands that are often referred to as "necklaces". Breeding females are similar in appearance but are overall duller. At the end of the breeding season, these birds molt into a duller version of the breeding plumage. The unique breastband fades in males and may disappear altogether in females.
Juvenile northern parulas are similar in appearance to wintering adults, but are more greenish-gray above and have shorter wing-bars. These young birds lack any breastband and the yellow throat and breast are not as extensive. (Moldenhauer and Regelski, 1996; Sibley, 2000)
Northern parulas are found across North and Central America. They are Neotropical migrants, so they live in different regions in each season. In the spring and summer, this species breeds across southeastern Canada and the northern United States, including Minnesota, Wisconsin, Michigan, New York, New Hampshire, and Maine. Below this range, there is a narrow band of states that northern parulas do not breed in. These warblers migrate through, but do not breed in, Iowa and southern Minnesota eastward to Massachusetts and New Jersey. Below this belt, Parula americana breeds in every state in the southeastern United States.
During the winter, these warblers are found in southern Florida, Caribbean Islands, and Bermuda. They may also be found in Mexico and portions of Central America from Veracruz to Honduras. (Moldenhauer and Regelski, 1996; Sibley, 2000)
Northern parulas are found in a variety of habitats depending on the season and location. They are forest-dwelling birds, but live in different habitats in their summer and winter ranges. In general, they are are more abundant in forests with high tree species diversity, tree canopy height, and percent canopy cover. Northern populations of northern parulas breed in mature, moist coniferous forests. Southern populations are found in mature, moist, bottomland forest, where hanging Spanish moss is common. Northern parulas construct pendulum-shaped nests in hanging vegetation and so are attracted to suspended clumps of moss or twigs that are found in moist spruce bogs or hemlock swamps. Outside of the breeding season, during migration and winter, northern parulas are found in a wide variety of habitats, such as pastures, agricultural fields, plantations, and a wide variety of forest types. (Ehrlich, et al., 1988; Moldenhauer and Regelski, 1996; Palmer-Ball, 1996)
Like most warblers, northern parulas are monogamous, meaning one male and one female pair up to breed and raise young. Little is known about mating displays or behaviors. (Ehrlich, et al., 1988; Moldenhauer and Regelski, 1996)
Northern parulas begin breeding shortly after migrating to their breeding grounds from their wintering range. Southern populations begin breeding in March while northern populations do not begin until mid-May. Due to the longer breeding season, southern populations frequently have two broods, but northern populations generally have just one.
After pair formation, the female selects a place for a nest. Northern parulas nest in hanging nests that are built by hollowing out a clump of vegetation, like hanging Spanish moss, and then lining it with soft fibers, animal hair, grass, and pine needles. Nest sites near water sources are preferred and many nests are found at the end of branches suspended over water. These nests average 7 cm in outside diameter. After building her nest, the female lays an average of 4 to 5 white or cream-colored eggs speckled with brown. After eggs are laid, the incubation period typically lasts 12 to 14 days and the young fledge at 10 to 11 days old. Currently the length of fledgling stage is unknown. Juvenile parulas may breed during the following breeding season at less than 1 year old. (Ehrlich, et al., 1988; Moldenhauer and Regelski, 1996; Palmer-Ball, 1996)
When males return to their breeding area, they set up and defend a territory for nesting. Females then arrive and set up a nest in that territory. Females build the nest, lay the eggs, and incubate them without any help from males. Although a male may bring food to a female on the nest. Females provide most of the care for their young, although males defend territories and help remove the waste of the young from the nest. Upon arriving on the breeding grounds, males establish territories and are known to aggressively defend them against intruders. The young fledge 10 to 11 days after hatching and remain with both parents for an unknown period of time until they are independent. (Ehrlich, et al., 1988; Moldenhauer and Regelski, 1996)
Average lifespan for northern parulas is unknown. The current longevity record is held by a 7 year old, recaptured individual. This species is not kept in captivity, so no captive lifespan data exists. Predation, especially during the nesting period, is likely the most common cause of mortality. Like most Neotropical migrants, many parulas perish after collisions with tall man-made structures during night migrations. (Klimkiewicz, et al., 1983; Moldenhauer and Regelski, 1996)
Northern parulas spend portions of each year in different regions. This species breeds in the eastern half of North America, but spends winters in Central America during the non-breeding season. Individuals may be seen migrating between these two regions in mixed-species flocks with other wood-warblers during the fall and spring. Migration typically takes place at night, although this species is usually active during the day. Many small woodland species are known for high activity levels and are constantly flitting about within vegetation. In contrast, northern parulas are more stationary and will often perch for periods of time in the upper canopy. (Ehrlich, et al., 1988; Moldenhauer and Regelski, 1996)
Northern parulas are relatively territorial birds during the breeding season and males are known to defend territories ranging in size from 0.16 to 0.40 hectares. (Moldenhauer and Regelski, 1996)
Northern parulas use mainly calls and physical postures to communicate. The most common call for this species is a rising, buzzy trill that abruptly ends with a short note of lower tone. This call is described as "trills up, falls over". A second call is a buzzy, rapid string of short phrases. Only males sing entire songs, which are used to attract mates and defend territories. Both sexes are capable of producing short chip notes which are often used to stay in contact with mates or young.
Male northern parulas are territorial during the breeding season. Threatened males may spread their wings and hold their bodies horizontally or swipe their bills against branches. If body postures and displays do not cause an intruder to retreat, the male will perform an aerial attack. (Moldenhauer and Regelski, 1996)
Northern parulas are insectivorous and forage mostly on terrestrial invertebrates, such as spiders, damselflies, locusts, true bugs, hoppers, aphids, beetles, caterpillars, flies, wasps, bees, and ants. Spiders and caterpillars are their most common prey. During the winter they may eat more beetles and include fruit, seeds, and nectar in their diet. Northern parulas catch prey by hovering over vegetation and grabbing prey from it. They have not been observed drinking water, but they may drink from small bodies of water or even drink dew drops. (Ehrlich, et al., 1988; Johnson, 2000; Moldenhauer and Regelski, 1996)
There are no formal records of predation on northern parulas. Red squirrels, blue jays, and snakes are all likely predators of this species, especially predators of eggs and young in nests. Northern parulas may exhibit mobbing behavior when a nest predator is near. (Moldenhauer and Regelski, 1996; Stevenson and Anderson, 1994)
Northern parulas are insectivorous and impact on local insect communities. Even though predation has not yet been reported, northern paruals probably serve as prey for several predators. (Moldenhauer and Regelski, 1996)
There are no known negative affects of northern parulas on humans.
There are no known economic benefits that northern parulas provide for humans. It is a popular bird with bird watchers, and seasonal migrations of this and other warblers can attract commerce to popular stopover areas.
Northern parulas are considered "least concern" by the IUCN Red List. This species inhabits a wide geographical range and the population appears to be increasing in some areas. However, northern parulas are no longer found in some places where they were previously found. In some places that have experienced increased levels of air pollution, hanging mosses have died, which are important for nest building. Clearcutting and bog draining have also significantly reduced the amount of preferred breeding habitats available. Though this species is of least concern, efforts should still be made to develop sustainable forestry practices and decrease air pollutants to increase habitat quality for this and other species. (Moldenhauer and Regelski, 1996)
Rachelle Sterling (author), Special Projects, George Hammond (editor), Animal Diversity Web Staff, Tricia Jones (editor), University of Michigan-Ann Arbor, ADW Zookeeper (editor), University of Michigan-Ann Arbor, Tanya Dewey (editor), University of Michigan-Ann Arbor.
Ehrlich, P., D. Dobkin, D. Wheye. 1988. The Birder's Handbook: A Field Guide to the Natural History of North American Birds. New York, NY: Simon and Schuster.
Johnson, M. 2000. Evaluation of an arthopod sampling technique for measuring food availability for forest insectivorous birds. Journal of Field Ornithology, 71/1: 88-109.
Klimkiewicz, M., R. Clapp, A. Futcher. 1983. Longevity records of North American birds: Remizidae through Parulinae. Journal of Field Ornithology, 54/3: 287-294.
Moldenhauer, R., D. Regelski. 1996. "Northern Parula (Parula americana)" (On-line). The Birds of North America Online. Accessed June 28, 2011 at http://bna.birds.cornell.edu/bna/species/215.
Palmer-Ball, B. 1996. The Kentucky Breeding Bird Atlas. Kentucky: University Press of Kentucky.
Sibley, D. 2000. The Sibley Guide to Birds. New York: Alfred A. Knopf, Inc.
Stevenson, H., B. Anderson. 1994. The Birdlife of Florida. Gainesville, FL: University Press of Florida.