SPECIES

Blackpoll Warbler Setophaga striata Scientific name definitions

William DeLuca, Rebecca Holberton, Pamela D. Hunt, and Bonita C. Eliason
Version: 1.0 — Published March 4, 2020
Text last updated June 4, 2013

Breeding

Phenology

Members of different age and sex classes arrive on Kent I., NB, at different times. Breeding males arrive 18 May–9 Jun; breeding females first seen 22–23 May (Eliason 1986b). Four of 7 males present in more than a single year arrived within the same 2-d period in second year. Males >1 yr old tend to arrive first, and yearling males later, with no overlap in the dates they are first observed singing on territories. One male arrived 17 d earlier in his 2nd year than he had as a yearling. Females arrive over a longer period than do males; some older females arrive before yearling males. Breeding males arrive on territories in Vermont and New Hampshire between 15 May and 29 May; first breeding females typically seen 2-3 days after males arrive (WVD, K. McFarland unpubl. data).

Pair Formation

May occur shortly after females arrive on breeding grounds, particularly in cases where their former mates have also returned; 1–3 wk elapsed between date female first observed on territory and date eggs were laid (BCE, WVD).

Nest-Building

On Kent I., NB, first nests built in late May (Eliason 1986b). In New Hampshire (2006-2009) and Vermont (1994-2003), first nests are typically built in late May or early June.

First Broods

Figure 4. On Kent I., NB, 68% (n = 31) of first clutches initiated in first 2 wk of Jun. Median dates of first clutch initiation were 6, 8, and 10 Jun over 3-yr period (Eliason 1986b). Latest date of a first nest 22 Jun. In New Hampshire, initiation dates ranged from 31 May to 8 Jul, with median date for nest initiation 10 Jun. In Vermont, initiation dates ranged from 30 May to 16 Jul, with median date for nest initiation 13 Jun. Some later nests may have been replacement nests if first attempts were destroyed before discovery.

In nw. Newfoundland (Dalley et al. 2009), median nest initiation dates: mid to late June; incubation period 11–12 d; young stay in the nest 8–10 d; fledglings near independence 25 d after leaving the nest.

Second Broods

On Kent Island, N.B, 65% (13 of 20) of females with known season-long breeding histories had 2 broods. Average interval between fledging of first broods and initiation of second clutch = 9.1 d (range 3–13, n = 14); latest fledging date 5 Aug; 93% of second clutches initiated in first 2 wk of Jul (BCE). Of 62 breeding pairs observed on Mt. Jefferson, NH, from 2006-2009 and of over 250 breeding pairs observed in Vermont from 1994-2003, no second brood attempts observed (WVD, K. McFarland pers. comm.).

Nest Site

Selection Process

Female moves from one spot in a tree to another and performs nest-building movements, but without nesting material. Once a specific location has been selected, female squats and flutters wings (WVD). May be lag of up to several days between observations of nest-site selection behavior and initiation of building. Male not known to participate in nest selection process (BCE), although males have been observed within 2-3 m of females while they are selecting the nest location (WVD).

Microhabitat

Twenty-four nests found on Kent I. and nearby Grand Manan I., NB, were in white spruce, most against the trunk of the tree (Bent 1953b). White spruce selected more frequently than would be predicted from its abundance in the habitat: of 35 nests, 32% in white spruce, 28% in red spruce, and 40% in balsam (about 9% of trees on territories were white spruce; Eliason 1986b). In Alaska, limited data suggest preference for nest sites with dense cover below 1 m (Kessel 1998).

In Vermont (Mt. Mansfield, Stratton Mt.; K. McFarland unpubl. data), 85% of nests were located in balsam fir, 15% in red spruce (n = 213). Of 37 nests on Mt. Mansfield, nest sites had significantly more red spruce and leaf litter within 5 m and less total green ground cover within 5 m compared to unused, random locations. On Mt. Jefferson, NH, 86% of 50 nests were located in balsam fir, 10% in dead trees (primarily balsam fir), and 4% in red spruce.

From 39 nests in w. Newfoundland (Dalley et al. 2008): 17 located in balsam fir, 12 in black spruce, 4 on moss, 2 on bare ground, 2 in snags, and 2 in other. Nest sites had more course woody debris, stems between 1-2 m high, stems >2 m, and less herbaceous vegetation >10 cm high within 1 m of the nest and more stems between 1-2 m high within 5 m of the nest, compared to random sites. Also, successful nests had more large downed wood within 5 m of the nest than did unsuccessful nests.

Site Characteristics

On Kent I., NB, 57% (n = 35) of first nests were against the trunk of the tree (Eliason 1986b). In Vermont, 61% of 113 nests were against the trunk of the tree; distance away from trunk ranged up to 2.5 m (K. McFarland, unpubl. data). In New Hampshire, 66% of 38 nests were located against the trunk; distance from the trunk ranged up to 2.6 m (WVD).

Nests are sometimes sandwiched between two trunks; occasionally on top of the horizontal trunks of downed trees, at the top of the main trunk of a dead standing tree, or supported by live or dead branches away from the trunk (BCE, WVD). On Grand Manan I., mean height of 1.5 m above ground (range 0.3–3.0 m, n = 15; Bent 1953b). On Kent I., mean height 2.5 m (range 0.6–5.3 m, n = 35); second nests higher than first, averaging 3.4 m (range 1.3–5.3 m, n = 13; Eliason 1986b). Mean height of nests on Mt. Cardigan, NH: 0.5 m (range 0.3–0.8 m, n = 4; PDH). Mean height on Mt. Jefferson, NH: 3.0 m (range = 0.2–10.0 m, n = 50); in Vermont, 1.2 m above ground (range = 0.2-7.0 m, n = 213). Of 24 nests in Alaskan shrub habitats, 62% <0.6 m and 42% below 0.3 m (Kessel 1998). Mean nest height in Newfoundland: 0.4 m (range = 0.0-2.0 m, n = 39; Dalley et al. 2008).

Nest

Construction

Only female builds, although male often follows female that is collecting nesting material and sings nearby while female builds. First nests are lined with feathers and moose hair (WVD) before first egg is laid; feathers are deposited after laying in some second nests. At 2 nests at which extensive observations were made during nest-building, periods of rapid trips (once every 2–3 min) were interspersed with periods when females were absent from the nest site for up to 30 min. Active nest-building usually lasted 3–4 d. By fourth day, trips were as infrequent as once every 25 min (Eliason 1986b).

Female carries nesting material in her beak. As the nest cup begins to take shape, female sits inside, rotating her body, and apparently moving her feet to form the cup. As she builds, she makes stroking motions along her sides with her beak (BCE).

Structure And Composition Matter

Open cup nest; usually coarser twigs form outside, followed by finer twigs, but in some cases lichen forms a significant component of the outer layer. Middle layer is often up to 50% lichen. Nest is lined with grasses and often with fine black plant fibers. All nests are lined with feathers (Harrison 1975b, BCE).

Dimensions

Outside diameter 10.7 cm (range 9–13) and height 6.8 cm (4–9, n = 31, BCE); inside diameter 5.3 cm and depth 3.4 cm (n = 4, PDH). In Vermont, outside diameter 10.3 cm, nest height 7.5 cm, inside diameter 6.0 cm, mean cup depth 3.9 cm, (n = 213).

Microclimate

On Kent I., NB, 50% of nests located between 180 and 269° relative to tree trunk, and only 7.5% between 270 and 359° (Eliason 1986b). Southwest-facing sites offer maximum protection from the sometimes intense storms that come from the Northeast (20% of nests in the NE quadrant, 0–90°). At this site, 3 instances of nestling mortality occurred after such storms.

In Vermont, 13% of nests located between 0° and 90°, 31% between 91° and 180°, 33% between 181° and 270°, and 23% between 271° and 360°. In New Hampshire, 13% of nests located between 0° and 90°, 32% between 91° and 180°, 37% between 181° and 270°, and 18% between 271° and 360°. South-facing nests may be more common in the mountains of Vermont and New Hampshire because they receive more direct solar radiation than north-facing ones, which may be important in damp, cool climates.

Maintenance And Reuse Of Nests

During incubation, female frequently pokes around in the nest and sometimes removes feathers. Reuse never reported; female builds a new nest for the second brood or for re-nesting after a failure (BCE, WVD).

Eggs

Mostly from Harrison 1975b.

Shape

Oval to long oval.

Size

Mean length 18.41 mm (range 16.51–20.35), mean breadth 13.61 mm (range 12.37–14.63, n = 93 eggs, 21 clutches, Western Foundation of Vertebrate Zoology [WFVZ]).

Mass

No information on whole eggs. Mean empty shell mass 0.093 g (range 0.073–0.109, n = 93, WFVZ).

Color

White, creamy buff, pale green; evenly speckled with brown spots; blotched with subdued shades of lavender concentrated at large end.

Surface Texture

Smooth, little gloss.

Eggshell Thickness

No information.

Clutch Size

Of 27 clutches from Kent I., 1 with 3 eggs, 5 with 4, and 22 with 5 (Eliason 1986b). Average clutch size of first nests 4.8 (range 3–5, n = 27); average clutch size of second nests 3.4 (range 3–4, n = 14, Eliason 1986b). Of 141 completed clutches in Vermont, mean clutch size 4.1 (range 2-5). Of 31 completed clutches in New Hampshire, mean clutch size 4.0 (range 2-5).

Egg-Laying

Information from Kent I., NB (Eliason 1986b, BCE) and Mt. Jefferson, NH (WVD). Because it is difficult to determine exactly when nest-building is completed, egg-laying is compared with date of nest initiation. Interval between nest initiation and laying of first egg is 8–10 d for earliest nests (those begun before 1 Jun). Eggs laid in later nests (after 10 Jun) and second nests as soon as 4 d after building is initiated. Eggs laid 1/d until clutch is complete. During the egg-laying period, male sings throughout the day. Female is often seen foraging in the vicinity of her singing mate, but the male is rarely seen near the nest during this period. Replacement of individual eggs has not been documented. In one case when eggs disappeared from a nest during incubation, the female was seen building a new nest within 2 d, and egg-laying began within 6 d of loss of the previous clutch. Intraspecific egg-dumping not reported.

Incubation

Onset Of Broodiness And Incubation In Relation To Laying

Female sits on the nest on the day the penultimate egg is laid, but for shorter, more irregular periods than on subsequent days (Eliason 1986b).

Incubation Patch

Female has a single incubation patch that develops over most of the abdomen and breast (BCE, WVD). Seasonal progression of brood patch development in Appendix 1.

Cloacal Protuberance

Male cloaca swells and enlarges similar to other wood warblers. See Appendix 1 for details.

Incubation Period

Lasts 11.5–12 d (Eliason 1986b, WVD).

Parental Behavior

Only female observed to incubate. Bent (Bent 1953b) reported that male Blackpoll Warblers typically feed females during incubation, but male provisioning of females was observed only infrequently on Kent I., NB (Eliason 1986b) and Mt. Jefferson, NH (WVD). In 190 h of observation at 7 nests during incubation, 4 males brought food a total of 6 times to their nests. In 3 of these instances, the male gave the food to the female. In the other 3, either the female was not present or the male refused to surrender the food to her, even though the female assumed an open-mouth begging posture. Such infrequent trips could not provide an important contribution to female nutrition. They may represent “anticipatory food-bringing,” in which the male comes to the nest with food, anticipating hatching of the eggs, and when they are not hatched, gives the food to the female (Nolan 1978).

Mean amount of time spent incubating increased with date from 37.6 min/h on day 1 to 49 min/h on day 11 for 3 females whose attentiveness patterns were systematically monitored. Time of day had a significant effect on incubation for only 1 of 3 birds; that female incubated less during the early-evening observation period than during the afternoon (Eliason 1986b). During incubation, female frequently reaches down in the nest and pokes with beak. At times, the movements were consistent with egg-rolling. At other times they seemed far more vigorous than would have been needed to accomplish that task (BCE).

Hardiness Of Eggs Against Temperature Stress; Effect Of Egg Neglect

No information.

Hatching

Preliminary Events And Vocalizations

Near end of incubation, female becomes increasingly restless, frequently standing, looking into nest, and sometimes poking with beak as described above (BCE).

Shell-Breaking And Emergence

Hatching can occur at any time of day. No good information on duration of hatching. Hatching patterns suggest that incubation usually begins before the last egg is laid. In all clutches of 4 or 5 in which all eggs hatched, hatching occurred over a 24-h period (n = 9; Eliason 1986b).

Parental Assistance And Disposal Of Eggshells

Female eats eggshell fragments while sitting on the nest during hatching (BCE).

Young Birds

Condition At Hatching

Altricial, eyes closed, small tuft of down on head only, bare parts yellowish. Mean weight of 1.5 g for young ≤1 d old (n = 16, Table 1). Young able to stretch and gape shortly after hatching (BCE).

Growth And Development

For measurements, see Table 1. Nestling shows pin-feathers on wings 3 d after hatching. Eyes fully open by day 5. Body-feathers begin to erupt from feather sheaths on day 6 or 7, and remiges erupt from sheaths on day 7 or 9. Audible vocalizations during handling are first heard on days 4–5. By day 8 nestling actively preens wings (Eliason 1986b). Late in nestling period, young stretch and rapidly beat wings; before nest-leaving, sometimes perch on edge of nest and flap wings (BCE, WVD).

Parental Care

Brooding

All information from Kent I., NB (Eliason 1986b). No abrupt change in behavior between end of incubation and beginning of brooding. At end of incubation, female incubates an average of 49 min/h. Mean brooding time drops from 47 min/h on day 2 after hatching to 5 min/h on day 8. Thirty-minute observation periods in which no brooding was observed first occurred on day 5. Day 6 was the first day that no brooding occurred at some nests during 90 min of observation. There was a trend for females mated to monogamous males to spend more time brooding both early (day 2–4) and late (days 6–9) in the nestling period, compared with either primary or secondary females of polygynous males. Females mated to polygynous males tended to stop brooding earlier than did females mated to monogamous males. By day 8, 5 of 7 (71%) females mated to polygynous males had stopped brooding, in contrast to 3 of 8 (37%) females mated to monogamous males. By day 9, all females mated to polygynous males and 6 of 8 (75%) females mated to monogamous males had stopped brooding.

As during incubation, male frequently sings near the nest, and female's departure from the nest often occurs when the male is nearby. Male also frequently accompanies female while she forages and returns to the vicinity of the nest briefly when the female returns.

With second broods, female tends to brood less both early and late in the nestling period than with first broods.

Feeding

All information from Kent I., NB (Eliason 1986b, BCE). Both male and female feed nestlings. Food carried to nest in beak by adults; young gape when adults arrive at nest and adults poke food down into mouth of young. Young are fed Lepidoptera larvae, spiders, and flies, based on direct observation from blinds. Sampling of food fed to nestlings has not been done.

For monogamous broods, pair trips/nestling/h increased from 1.4 to 4.1 on days 2–8, and then dropped to 3.7 on day 9. Pair feeding rates, when corrected for brood size, were not significantly different for pairs of different mating status. Monogamous males made more trips/nestling than did females early in the nesting period, and the same number of trips during the rest of the nestling period. Polygynous males fed more at nests of one female (designated the primary female) than at the other (designated the secondary female). At primary nests, males and females made about the same number of trips each day. Secondary females made many more trips than did their mates on all days except day 2, when males and females made similar numbers of trips. The average proportion of trips made by monogamous males for days 2–9 was 53.9%, for males to nests of primary females 48%, and for males to nests of secondary females 19%. Males were more likely to feed secondary nestlings when there was extensive overlap with primary nests. Where there was less overlap, males were involved in the demanding task of feeding fledglings from their primary females while their primary females initiated their second broods, leaving less time to feed the nestlings of their secondary females.

Timing of broods may also explain why females perform a larger proportion of nestling feeding trips to second broods than to first broods. The greater effort of females in caring for second brood nestlings may be related to the fact that some males were still feeding first brood fledglings when second nests hatched.

Size and number of items/trip increase with nestling age, but there are no quantitative data on this. Polygynous males brought a larger proportion of small loads to both of their nests than did monogamous males. However, indices of mean load size were only slightly less for polygynous males than for monogamous males, indicating that the number of trips made was approximately representative of male contributions. Females mated to monogamous males brought a larger proportion of small loads than did mates of polygynous males. When data from males and females were pooled, mean indices of load sizes were similar at all 3 types of nests (list from above). Food appears to be distributed in response to the vigor of begging.

Nest Sanitation

Like other passerines, young produce fecal sacs, usually in response to delivery of food. Parents sometimes eat fecal sacs of very young nestlings; later parents carry off the sacs in their beaks. Late in the nestling period, nestlings can be observed elevating their rumps toward the nest edge before defecating (BCE, WVD).

Parental Carrying Of Young

Not reported for this species.

Cooperative Breeding

On one occasion on Kent I., NB, an unmated male was frequently observed in the vicinity of the nest of a female who was mated to a polygynous male. This male subsequently was observed feeding fledglings from this nest, and was the only male seen feeding nestlings of this female's second brood (BCE). On Mt. Cardigan, NH, a male of uncertain mating status was once observed bringing food to the vicinity of a neighboring pair's nest (PDH). Of 50 nests on Mt. Jefferson, two were observed to have two males deliver food to nestlings. In one instance, the helper at one nest also had another nest that received most of his food delivery efforts. The frequency at which the unbanded male delivered food to this nest was unknown (WVD). The frequency of such behavior in this species is unknown, but it seems unlikely to be a viable reproductive strategy and may simply be a result of high breeding densities at the above sites. Alternatively, it may represent a male's attempt to influence mate selection by a given female in the following breeding season (BCE).

Brood Parasitism by Other Species

Rare host of the Brown-headed Cowbird (Molothrus ater). Of >1,200 cases of parasitism listed by Bull (Bull 1974), only one pertained to the Blackpoll Warbler. No recorded parasitism on 41 nests on Kent I., NB (BCE), 213 nests in Vermont, or 50 nests in New Hampshire (WVD). It seems unlikely that cowbirds penetrate often into the Blackpoll Warbler's usually remote or high elevation breeding habitat.

Fledgling Stage

Departure From The Nest

On Kent I., NB (Eliason 1986b, BCE), for broods in 20 nests found before hatching, 12 fledged on the tenth day after hatching, 6 fledged on the ninth day, and 2 fledged on the eighth day. In 12 of 20 broods, all young left the nest over a 12-h period, whereas 8 of 20 broods left the nest over a ≥24-h period. Hatching asynchrony in Blackpoll Warblers may be responsible for asynchronous fledging. In New Hampshire, for 16 successful nests found before hatching, 8 fledged on the tenth day, 7 fledged on the ninth day, and 1 fledged on the eighth day (WVD).

Young leave the nest before they are able to fly strongly. Toward the end of the nestling period, they become increasingly active, sometimes hopping to the edge of the nest and flapping their wings. Occasionally a nestling will hop from the nest to an adjacent branch, remain there for up to several minutes, and return to the nest. Leaving the nest, a chick hops, or sometimes falls, from the rim and flutters to lower branches or the ground. In cases where a chick lands on the ground, an adult has been observed “leading” it onto low branches by repeatedly approaching, chipping, and then hopping into the tree itself.

Growth

No information.

Association With Parents Or Other Young

See below.

Ability To Get Around, Feed, And Care For Self

All information from Kent I., NB (Eliason 1986b). Fledglings fed for up to 25 d after leaving the nest, although they begin trying to catch their own food as early as day 8 after fledging. Fledglings can fly strongly 9 d after fledging, and begin to wander widely off the territory after 20–25 d. The Blackpoll Warbler dependency period at this site may be shorter than that of congeners because of the prevalence of second broods.

Adult males were observed feeding first-brood fledglings more often than were females. In 125 observations of fledglings from 11 broods being fed, in 80.8% (101) of the instances, the male parent was doing the feeding. For 6 of 11 broods, the female was never seen feeding the fledglings. For 2 broods, only the female fed fledglings; these were secondary females of polygynous males.

Observations of fledglings being fed may be slightly biased toward groups fed by the male parent because family groups were usually located by their vocalizations, and the male sometimes sings while foraging. Both parents were observed feeding the same fledgling in 3 broods. The male assumes care of all first-brood fledglings when the female begins incubating second broods.

Immature Stage

All information is from the boreal forests of nw. Newfoundland, Canada (Mitchell et al. 2009, Mitchell et al. 2010). The movements of 46 postfledging Blackpolls were mapped using radio telemetry (Mitchell et al. 2009). The range of the median movement rate was 4 – 7,380 m/d and rates increased through the end of July and into August. Post-fledglings spent less time when local (5 m) and neighborhood (115 m) areas were clearcut compared to forest. Clearcut land cover was also found to impede landscape connectivity as post-fledglings moved from harvested areas. In a separate study, Mitchell et al. (2010) used radio telemetry to track to 26 birds captured in clearcut landscapes and 22 birds captured in nonharvested landscapes. At the local scale, postfledgling blackpolls were associated with dense understory vegetation, foliage density, and coarse woody debris. Individuals were observed on the ground or in understory vegetation at 16% of locations. Post-fledglings were positively associated with clearcuts when ≤5% land within 1,250 m was clearcut, but when >5% of the landscape was clearcut at this scale, the relationship was negative. No information is available in unmanaged forests.

Blackpoll Warbler Fig. 4. Annual cycle of breeding, molt, and migration of the Blackpoll Warbler.
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Fig. 4. Annual cycle of breeding, molt, and migration of the Blackpoll Warbler.

Thick lines show peak activity; thin lines, off-peak.

Blackpoll Warbler Blackpoll Warbler nest, Quebec.
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Blackpoll Warbler nest, Quebec.

Magdalen Is., Quebec. 8 July. Ruler is in cm.; photographer Rene Corado

Blackpoll Warbler Blackpoll Warbler clutch; Grand Lake, Newfoundland.
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Blackpoll Warbler clutch; Grand Lake, Newfoundland.

Collected 24 June. Ruler is in cm.; photographer Rene Corado

Recommended Citation

DeLuca, W., R. Holberton, P. D. Hunt, and B. C. Eliason (2020). Blackpoll Warbler (Setophaga striata), version 1.0. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.bkpwar.01