Parula americana
northern parula

Commonly known as northern parulas, Parula americana is found across the Nearctic and Neotropical regions. As a Neotropical migrant, Parula americana inhabits different regions in each season. In the spring and summer, this species breeds across the southeastern edge of Canada including the southern portions of Manitoba, Ontario, Quebec, and Maritime Provinces. This northernmost breeding range includes Minnesota, Wisconsin, Michigan, New York, New Hampshire and Maine. Below this range, there is a narrow band of states that Parula americana does not breed in. This warbler migrates through, but does 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 inhabits the very southern tip of 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)

Parula americana inhabits various habitats depending on season and location. This is primarily a forest-dwelling species, but the northern and southern breeding populations select different habitats. In general, abundance of this species has been found to be positively correlated with increased tree species diversity, canopy height, and percent canopy cover. Northern populations breed in mature, moist coniferous forests. This species constructs its pendulum nests in hanging vegetation and so it is often attracted to suspended clumps of moss or coniferous twigs that are more abundant in moist spruce bogs or hemlock swamps. Southern populations breed in mature, moist, bottomland forest where Spanish moss is prevalent.

Outside of the breeding season, Parula americana becomes more of a habitat generalist and may be found in a wide variety of habitats during migration and winter. These habitats may include: pastures; moist, dry or wet forests; and agricultural fields or plantations. (Ehrlich, et al., 1988; Moldenhauer and Regelski, 1996; Palmer-Ball, 1996)

Parula americana is a small wood-warbler that measures 11.4 cm in length and weighs 8.6 g. This species molts twice annually, 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 bill is two-toned, with a black upper mandible and a yellow lower mandible that blends with the yellow throat. The bellies and undertail coverts are unmarked white. 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, individuals molt into a duller version of the breeding plumage. The unique breastband fades in males and may disappear altogether in females.

Parula americana juveniles 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)

Like most warblers, Parula americana is a monogamous species, however, a few cases of polygamy have been reported. Little is known about mating displays or behaviors and more research is needed in this area. (Ehrlich, et al., 1988; Moldenhauer and Regelski, 1996)

Parula americana is a Neotropical migrant that begins breeding shortly after arriving at the breeding grounds. Arrival dates vary with geographic location, but 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, as opposed to northern populations which have one.

After pair formation, the female selects a suitable nest location within her mate's territory. Parula americana nests in hanging pendulum shaped nests, usually located in hanging epiphytes such as Spanish moss. Sites located near water sources are preferred and many nests are found at the end of branches suspended over water. Females complete most of the nest construction with little to no help from males. The female hollows out a clump of vegetation and proceeds to fill the cavity with vegetation fibers, animal hair, grass, or pine needles. 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 varying amounts of 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 the fledgling stage is unknown. Juvenile northern parulas may breed during the following breeding season. (Ehrlich, et al., 1988; Moldenhauer and Regelski, 1996; Palmer-Ball, 1996)

Upon arriving on the breeding grounds, males establish territories and aggressively defend them against intruders. The male is responsible for selecting a suitable territory and defending and protecting his territory, mate, and young. After pair-formation, the female selects a nesting site within her mate's territory and constructs the nest with little to no help from the male. The female then lays the clutch and is the sole incubator. The male occasionally assists by feeding the female while she broods the clutch. After the young have hatched, the female continues to perform most of the parental care. The female performs all brooding and most of the feeding. Both parents participate in nest sanitation and remove fecal sacs to prevent disease or reduce chance of predation. The young fledge 10 to 11 days after hatching and will remain under both parents' care for an unknown period of time. The female performs most of the feeding, but the male remains near to sing and defend his brood. (Ehrlich, et al., 1988; Moldenhauer and Regelski, 1996)

The average lifespan for Parula americana is currently unknown. Current longevity record is held by a 7 year old, recaptured individual. Previously the longest lived bird was a recaptured female estimated at 4.5 years old. As this species is not kept in captivity, 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)

As a Neotropical migrant, Parula americana spends portions of each year in different regions. This species breeds in the eastern half of North America, but overwinters 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 diurnal for all other activities. Many small woodland species are known for high activity levels and are constantly flitting about within vegetation. In contrast, Parula americana is more stationary and will often perch for periods of time in the upper canopy. (Ehrlich, et al., 1988; Moldenhauer and Regelski, 1996)

Parula americana is a relatively territorial species during the breeding season and males are known to defend territories ranging in size from 0.16 to 0.40 hectares. Like most birds, territory size is influenced by resource availability, however territory size for Parula americana is known to increase with increased presence of American beech (Fagus grandifolia) or stand size. (Moldenhauer and Regelski, 1996)

Parula americana communicates mainly through a combination of vocal calls and physical movements or postures. The primary call for this species is an ascending, buzzy trill that abruptly ends with a short note of lower tone. This call is aptly described as "trills up, falls over". Parula americana also gives a second call that is a buzzy, rapid string of short phrases that varies in length. Only males sing entire songs, which are used to establish or defend territory, as well as to attract mates. Males seem to use the primary call for attracting or interacting with females, while the more rapid calls are used in territorial disputes. Both sexes are capable of producing short chip notes which are often used to stay in contact with mates or young.

Male Parula americana are highly territorial during the breeding season, and use a combination of calls and physical displays to deter competitors. Threatened males may spread their wings while also holding their bodies horizontally. Males also vigorously swipe their bills against perches when intruders are nearby, which is likely a threatening display. If body postures and displays do not cause the intruder to retreat, the defending male will perform an aggressive aerial attack. Like most birds, Parula americana perceives its environment through visual, auditory, tactile and chemical stimuli. (Moldenhauer and Regelski, 1996)

Parula americana is an insectivorous species, that forages mostly or entirely on terrestrial invertebrates. Prey items include spiders, damselflies, locusts, true bugs, hoppers, aphids, beetles, caterpillars, flies, wasps, bees, and ants. Regardless of season, caterpillars and spiders are consumed most often. During the winter, Parula americana consumes more beetles and occasionally forages on berries, seeds, and nectar. Parula americana primarily captures prey from vegetation by a hover-glean method, however this species is versatile in using a variety of foraging methods. It may make short flights from a perch to snatch prey in mid-flight or even hang upside-down to forage. It is most often seen foraging in the mid- to upper canopy levels of vegetation. Though most foraging activity occurs in vegetation, this species occasionally forages on the ground as well. (Ehrlich, et al., 1988; Johnson, 2000; Moldenhauer and Regelski, 1996)

Currently there are no formal records of predation on Parula americana. Red squirrels, blue jays, and snakes are all likely predators of this species, especially predators of eggs and young in nests. Parula americana may exhibit mobbing behavior when a nest predator is near. (Moldenhauer and Regelski, 1996; Stevenson and Anderson, 1994)

Parula americana is an insectivorous species and thus likely has an impact on local insect communities. Although predation has not yet been reported, Parula americana probably serves as prey for several predators. (Moldenhauer and Regelski, 1996)

There are no known economic benefits that Parula americana provides 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.

There are no known negative affects of Parula americana on humans.

Parula americana is considered "least concern" by the International Union for Conservation of Nature and Natural Resources' (IUCN) Red List. This species inhabits an expansive geographical range and the population appears to be increasing. Despite this abundance, Parula americana has been extirpated from several regions where it previously bred. Massachusetts, New Jersey, Connecticut, New York, Rhode Island, and Vermont have recently experienced increased levels of air pollution and have consequently lost most of the epiphytes that this species prefers to nest in. 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)