CR (PE)
Bachman's Warbler Vermivora bachmanii



Justification

Justification of Red List Category
This last confirmed breeding record of this species was in 1937, and it has not been reported since 1988. It may have gone extinct as a result of habitat destruction both on the breeding and wintering grounds. However, it cannot yet be presumed to be Extinct until all remnant patches of possible breeding habitat have been searched, and unconfirmed reports have been followed up. Any remaining population is likely to be tiny, and for these reasons it is treated as Critically Endangered (Possibly Extinct).

Population justification
Any remaining population is assumed to be tiny (numbering fewer than 50 individuals and mature individuals), with the last (unconfirmed) sighting in 1988.

Distribution and population

Vermivora bachmanii is known to have bred in Missouri, Arkansas, Kentucky, Alabama and South Carolina, USA, and there are breeding-season records from various other south-east states. Birds wintered in Cuba and occasionally Florida, USA. The last nest was found in 1937, but there have been more recent (unconfirmed) sightings (D. Peterson in litt. 2012, K. Rosenberg in litt. 2003). Small areas of suitable habitat remain, and the species may still survive (Curson et al. 1994).

Ecology

It bred in seasonally flooded swamp-forest, always near standing water (Curson et al. 1994), apparently showing a strong association with canebrakes of the bamboo Arundinaria gigantea, and blackberry (Pulliam 2010). Like the closely-related V. cyanoptera and V. chrysoptera it may have been a bird of gaps, edges, and early-mid successional habitats within the forest mosaic (although bachmanii had more of a preference for forest canopy), and it apparently did not require primeval swamp forest: the last documented breeding site had previously been a rice field some decades before (Pulliam 2010). Winter habitat requirements were much less specific, with records from dry forest, wetlands and urban areas (Hamel 1995), but apparently favouring wooded areas with flowering Hibiscus trees (Curson et al. 1994). Breeding occurred from March-June, with the nest constructed in the shelter of a dense bush or tangle of vegetation (Curson et al. 1994). Migrants were seen in Peninsular and insular Florida in early spring and late summer (March-April and July-August; Pulliam 2010).

Threats

The drainage of river-bottom swamplands (Curson et al. 1994), and the near-total clearance of canebrakes in the USA, combined with the conversion of much of Cuba to sugarcane plantation, offer the best explanation for the disappearance of this species.

Conservation actions

Conservation Actions Underway
There is currently no action being taken for this species. Searches within the large expanses of suitable habitat that remain on the wintering grounds would be costly and most probably futile (A. Mitchell in litt. 1998).

Conservation Actions Proposed
Systematically search any potentially suitable habitat with thick canebrake and blackberry brush within the (former) breeding range; including that away from historic sites, which may no longer be suitable (Pulliam 2010). Follow up any reports of birds within the breeding range, on passage, or on the wintering grounds.

Identification

12 cm. Delicate warbler with slender, decurved bill. Adult male, black forecrown, grey hind-crown and nape, yellow forehead, eye-ring, lores, supercilium and throat. Yellow underparts with black patch on upper breast and white undertail. Olive-green upperparts, grey wings with olive fringes and yellow lesser coverts, grey tail with white spots on inner webs of all but central rectrices. First-year male, duller with indistinct black breast patch and no black forecrown. Adult female, duller with whitish eye-ring, no black and less well marked head. First year female, even duller and paler below. Juvenile, brownish, buffy-yellow below, whiter on throat, two buffy wing-bars. Similar spp Hooded Warbler Wilsonia citrina differs from female by bill, eye-ring, and grey crown contrasting with nape and forehead. Voice Song a buzzy, pulsating, insect-like trill, sometimes given in song flight. Call a low, hissing zee e eep.

Acknowledgements

Text account compilers
Bird, J., Butchart, S., Pople, R., Sharpe, C J & Symes, A.

Contributors
Budney, G. & Rosenberg, K.


Recommended citation
BirdLife International (2018) Species factsheet: Vermivora bachmanii. Downloaded from http://www.birdlife.org on 17/01/2018. Recommended citation for factsheets for more than one species: BirdLife International (2018) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 17/01/2018.