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

Demography and Populations

Measures of Breeding Activity

Age At First Breeding; Intervals Between Breeding

Of 12 known yearling males, 4 were known to breed (minimum estimate: some may have bred outside study area). All birds ≥2 yr old breed each year (BCE). On Mt. Jefferson, NH, several second year males were observed breeding while there were also several ASY males that were not believed to be paired. These individuals sang throughout the breeding season and were likely attempting to attract a mate; however, their territories were typically located at lower elevations and were thus believed to lower quality habitat (WVD).

Clutch

Typically 4–5 eggs (see Breeding: eggs, above). On Kent I., NB, 65% of females had 2 broods; average clutch size of first nests 4.8 (range 3–5, n = 27); of second nests 3.4 (range 3–4, n = 14, Eliason 1986b). Females ≥2 yr old laid significantly more eggs/year (mean 7.9, range 4–9, n = 11) than did yearling females (mean 5.8, range 3–8, n = 4; Eliason 1986b).

Annual And Lifetime Reproductive Success

On Kent I., NB, 90% (164/182) of eggs hatched (BCE); 83% (151/182) of eggs produced fledglings. All first nests (n = 33) produced at least one fledgling, i.e., were “successful.” The mean number of fledglings produced in first nests was 3.8 (range 1–5, n = 28). Thirteen of 14-second nests (93%) were successful. The mean number of fledglings produced in second nests was 3.08 (range 0–4, n = 12). Nesting success for all 48 first and second nests was 98%. Average annual reproductive success was 5.6 young/female (range 3–9, n = 19). Average annual reproductive success for mated males was 6.3 (range 3–13, n = 17); for all males 5.3 (range 0–13, n = 20). Females that attempted two broods fledged 6.6 young/season (n = 13), whereas those that did not fledged 3.7 young/season (n = 6). All females on Kent I. reared at least one brood to nest-leaving age. On Kent I., NB, the minimum annual reproductive success of any female was 2 fledglings (Eliason 1986b).

In Vermont, 62% (284/458) of eggs hatched; 58% (265/458) of eggs produced fledglings (n = 109 nests, K. McFarland unpubl. data). Daily nest survival was 96.7% and overall nest success was 43.7%. On Mt. Jefferson, NH, daily nest survival was 96.7% and overall nest success was 42.7%, n = 49; WVD).

Annual reproductive success of both males and females on Kent I. was related to mating status. Polygynous males produced 11.3 young/season (range 10–13, n = 4), monogamous males 4.8 (range 3–8, n = 13), a significant difference. Among females, primary females produced the most fledglings/season (8.3, n = 4), and secondary the fewest (4.8, n = 4). Monogamous females produced 5 fledglings/season (n = 11; Eliason 1986b).

Age also influenced the number of young fledged in a season, with older birds more successful than yearlings. This was especially true for males: second-years (SYs) averaged 2.5 fledglings/year (range 0–6, n = 7), while older (ASY) males averaged 6.2 (range 3–12, n = 11). Among females, SYs and ASY females averaged 4.6 (range 3–7, n = 4) and 5.9 fledglings/year (range 3–9, n = 11), respectively (Eliason 1986b). On Mt. Jefferson, NH, SY males averaged 2.3 (range 0-4, n = 4) and ASY males averaged 2.9 (range 0-5, n = 11; WVD unpubl. data).

Limited information on lifetime reproductive success. One female present 4 summers on Kent I. fledged 22 young (BCE).

Number Of Broods Normally Reared Per Season

On Kent Island, N.B, 65% (13 of 20) of females with known season-long breeding histories had 2 broods. The incidence of second broods is much higher than in some congeners, such as Prairie Warblers (S. discolor; 18/86 successful nests or 21%; Nolan 1978). Despite the shorter breeding season at high latitudes, low rates of nest predation at this site may allow many Blackpolls to complete their first nestings early enough to raise second broods. Females that had second broods initiated their first nests significantly earlier than those that did not have second broods. No female that initiated her nest >10 d after the first egg of the season was laid had a second brood (Eliason 1986b).

Of over 300 breeding pairs observed in Vermont and New Hampshire, no second brood was documented after a successful nesting attempt (See Breeding). The lack of second brood attempts may be due to the comparatively lower success rates of initial nesting attempts than on Kent I. (See Reproductive Success).

Life Span and Survivorship

Limited life span information (max based on band recovery/resighting): 5 yr (PDH, WVD); 4 yr (Klimkiewicz et al. 1983); 8+ for males, 7+ for females (BCE). No data on survivorship.

Disease and Body Parasites

No information on diseases. Feather mites observed. Internal parasites include blood protozoa Leucocytozoon and Haemoproteus (Bennett et al. 1988). Listed as a host species for avian malaria (Ricklefs et al. 2004).

Of 54 individuals sampled for blood parasites during the breeding season in Vermont montane fir forests, 7.4% were found to be infected with Plasmodium, 1.8% with Haemoproteus, 37% with Leucocytozoon, 11% with Trypansoma, and 5.5% with microfilarial worms (E. Martinsen, K. McFarland, C. Rimmer, S. Frey unpubl. data).

Causes of Mortality

Exposure

On Kent I., NB, one young at each of 2 nests died of presumed starvation (deduced from the fact that they lost weight and disappeared from the nest). Three young at one nest and 2 at another died after a severe thunderstorm, presumably of exposure (Eliason 1986b).

Breeding abundance was found to be negatively correlated with the number of days with storms over the Atlantic Ocean the preceding fall (Butler 2000), suggesting that oceanic storms may be a significant source of mortality.

Predation

See Behavior: predation, above. No adult mortality documented during 4 breeding seasons on Kent I., NB (BCE) and on Mt. Jefferson, NH (WVD). However, Sharp-shinned Hawks are known to prey on nests on Mt. Jefferson and may also prey on adults.

Competition With Other Species

Not known as a source of mortality.

Direct Human Impacts

Collides with towers, lighthouses, buildings, and other tall human-made structures during migration, with such collisions sometimes being a major source of mortality (Bent 1953b, Kale II et al. 1969, Roberts and Tamborski 1993, Kemper 1996a). For more detailed treatment see Conservation and Management: effects of human activity, below.

Population Spatial Metrics

Initial Dispersal From Natal Site

On Kent I., 14 of 20 locally hatched birds (banded as nestlings) returned to the area in a subsequent season (Eliason 1986b), and 1 of 12 nestlings returned to Mt. Cardigan (PDH). These levels of natal-site fidelity are quite high compared with those in other studies of passerines, perhaps a result of the insular nature of the breeding habitat where these data were collected.

Fidelity To Breeding Site And Winter Home Range

Banded males returned to Kent I., NB, at rates ranging from 27% to 75% (n = 34). The return rate of banded females ranged from 33% to 58% (n = 29, Eliason 1986b). Return rates of males to Mt. Cardigan, NH, ranged from 40% to 70% over 4 yr (PDH). Return rates of males on the Mt. Jefferson, NH site ranged between 47% and 61% over a 4-year period. These results are based on small sample sizes.

On Kent I., when males with known breeding histories returned in a subsequent year, they defended territories that included all or part of the territory they defended in the previous year. In 11 of 12 cases where females with known breeding histories returned, they settled on or immediately adjacent to the territory on which they had nested the year before (Eliason 1986b). Similar site fidelity was observed in the banded population on Mt. Cardigan, NH, where only 1 of 16 returning males was observed to move its territory location, irrespective of reproductive success the previous year (PDH). On Mt. Jefferson, NH, returning males typically returned to within 200 m of previous breeding territory, but new territories did not necessarily overlap with previous territories (WVD).

The only information from the winter range concerns an individual that remained in a limited area in Brazil from late Jan to early May (Sick 1971).

Dispersal From Breeding Site Or Colony

No information.

Home Range

For 33 individuals radio-tracked in 2004 and 2005 in w. Newfoundland, the 90% isopleth of their territory averaged 3.0 ha (0.5-7.9 ha) and the 90% isopleth of their home range averaged 4.3 ha (1.2-33.2 ha; Leonard et al. 2008). Average territory size on Mt. Jefferson, NH was 0.89 ha (n = 49, range 0.41-1.26 ha, WVD unpubl. data).

Population Status

Numbers

Usually one of the most common birds in subalpine habitats in the ne. U.S. (Able and Noon 1976). Density estimates from montane populations in the Northeast range from 1.5 pairs/10 ha at 750 m (Morse 1979a) to >40 pairs/10 ha in subalpine valleys (Sabo 1980). Densities average lower along ridgelines (Sabo 1980) or near tree line (Morse 1979a, PDH, WVD). At nine sites in Vermont and NY State, densities averaged 2.5 pairs/ha with a range of 1.3 – 4.7 (K. McFarland unpubl. data).

Lowland populations in New Brunswick range from 0.1 pair/10 ha in a young spruce plantation (Parker et al. 1994a) to 9.8 pairs/10 ha on Kent I. (Eliason 1986b). Few data for the central portion of the range, with estimates of 0.1–1.7 pairs/10 ha in various spruce and bog habitats across Canada (Errington 1933). These values are based on limited samples, however, as much breeding habitat in Canada is inaccessible (A. Erskine pers. comm.).

In western portions of the range, densities are usually higher in deciduous habitats than in conifers. In the Yukon, densities of 1.5–3.25 males/10 ha in willow habitats and 0.75–1.5 males/10 ha in spruce (Theberge 1976). In Alaska, 2.5–4.4 territories/10 ha in cottonwood-birch and 0.8–2.0 territories/10 ha in spruce (Kessel 1998).

Density estimates on the winter range are unavailable, but the species is reported as uncommon in w. Venezuela (J. Jones pers. comm.). The size of the isolated Pennsylvania population was estimated at 15-25 pairs (D. Gross, pers, comm.).

Trends

Figure 5. The bulk of the species' range falls outside the area covered by the Breeding Bird Survey (BBS), resulting in limited information on population trends. Survey-wide trends for the BBS indicate a non-significant decline of 5.8%/year from 1966-2009 (Sauer et al. 2011).

Declines tend to be somewhat larger in the southeastern portion of the range (e.g., New England, Maritime Canada), where they range from 5-15% annually (Environment Canada 2010, Sauer et al. 2011). Trends in central and western Canada tend to be in the 2-6% range, but relative abundance there is relatively low, and trends are often based on a small number of routes.

In an earlier analysis of BBS data, Sauer et al. (2008) showed increasing populations in the e. U.S. and e. Canada from 1966 to 1979, but a significant annual decline (-9.6) from 1980-2007. This same analysis indicated significant declines in Alaska (-2.9%) and Newfoundland (-6.9%), although these were again based on few data (e.g., poor “regional credibility” score, Sauer et al. 2008).

In summary, the species presently appears to be undergoing a widespread decline; more data on the spatial and temporal nature of the decline would clearly be valuable (see below).

Monitoring efforts focused on appropriate breeding habitat in the southeastern portion of the range yield equivocal results. High elevation surveys conducted across the ne. U.S. show an overall non-significant decline with considerable regional variation (Hart 2010). The trend was negative in the Adirondacks of NY (-6.0%) and Green Mountains of VT (-3.1%), but positive for the White Mountains of NH (5.9%). An independent data set in similar habitat in the White Mountains from 1993-2003 indicated a stable population there (King et al. 2007). Similar monitoring in Maritime Canada during 2002-2011 showed an increase of 9.1% in New Brunswick and a decrease of 9.3% in Nova Scotia, although the trends showed considerable regional variation within each province (Campbell and Stewart 2012).

Migration data also show no consistent pattern, with significant increases at Long Point, Ontario (>2%/yr, 1967-2004, Crewe 2006), and significant decreases (1.3%/yr over 49 yr) in e. Massachusetts (Hill and Hagan III 1991, Hagan et al. 1992, Llyod-Evans and Atwood 2004). Of 12 stations analyzed from 1997-2006 in Canada during fall migration, six reported negative trends, two of which were significant (-8.0%/yr and -18.8%/yr). All five locations within the Prairie region (central) had negative trends. Two of the six stations with positive trends were also significant (18.3%/yr and 2.2%/yr; Crewe et al. 2008)

Population Regulation

Little information. Although the species has been proposed as a possible spruce budworm specialist (Robbins et al. 1986a), available data show no relationship between Blackpoll Warbler numbers and budworm outbreaks (Morris et al. 1958). Abundance data collected during fall migration in Ontario show patterns of increase and decrease similar to those for known budworm specialists, although the magnitude of these changes was substantially lower and not significant (Hussell et al. 1989). The Blackpoll was not included in an analysis of warbler vagrancy patterns in relation to spruce budworm outbreaks (Patten and Burger 1998). More detailed analysis of migration data may shed light on the effect of budworm population cycles on Blackpoll Warbler populations.

Storms over the Atlantic Ocean during fall migration may regulate populations. Butler (2000) found that, over a 15-year period, Breeding Bird Survey estimates of Blackpoll abundance were negatively correlated with the frequency of storms over the western Atlantic Ocean.

Blackpoll Warbler Figure 5. Regional trends in Blackpoll Warbler populations; data from the Breeding Bird Survey, 1996-2003.
Enlarge
Figure 5. Regional trends in Blackpoll Warbler populations; data from the Breeding Bird Survey, 1996-2003.

Data show best estimates of population change for the species in the southern reaches of its range; from Sauer et al. 2008, which provides details.

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