KIRTLAND’S WARBLERS: ABACO’S RARE TREASURES

This is a challenging topic that I have been (shamefully) putting off. My task is a full-scale facing-up to an extremely rare, very small, and rather adorable adversary, the Kirtland’s Warbler (Setophaga kirtlandii). There are probably more dedicated KIWA experts out there than there are birds of this scarce species. Estimates of bird numbers vary wildly, but if I take a consensus of the mean of an approximate average of the median as ± 5000 individuals, I’d probably be in the ballpark named “Current Thinking“. 

THAT SOUNDS QUITE RARE, RIGHT?

Around 50 years ago, the species was all but extinct – perhaps fewer than 500 birds in total, a barely sustainable population. In 1975, Brudenell-Bruce estimated 1000. I’ll mention some of the reasons later. In the 1970s, the Kirtland’s Warbler Recovery Plan was instituted with the twin objectives of protecting the vulnerable breeding habitat – basically large areas of jack pine; and of monitoring and management aimed at encouraging an increase in numbers. Around that time, they became IUCN listed as vulnerable, but more recently, population growth has resulted in a recategorisation to the more optimistic near-threatened category.

AND THEY LIVE  WHERE, EXACTLY?

In spring and summer almost the entire KIWA population lives and breeds in very specific areas of Michigan and Ontario, where jack pines are found. There are signs that the range has expanded slightly in Michigan and more widely into Wisconsin and Ohio as the numbers have increased.

A Kirtland’s Warbler in the jack pines of Michigan (Vince Cavalieri)

In the fall and winter the population migrates to the Bahamas & TCI, where they tend to choose remote scrub and coppice areas to live until the spring when they return north in April. This range map shows the extremely specialist habitat choices of these migratory birds.

A Kirtland’s Warbler in Ohio 

SO THEY ARE REALLY FOUND ON ABACO?

Yes – but they are notoriously hard to find. To give you an idea, I checked the eBird stats for Abaco sightings over the last 10 years: 9 successful trips reported, with 18 birds seen in all**.  There were 3 groups comprising 6, 4, and 2 birds; and the rest were single birds. Abaco ornithologist and guide Woody Bracey is the go-to man for finding these little birds. Two years ago we were in his party that saw 4 in the space of a couple of hours. I was supposedly the photographer, but unaccountably found myself in completely the wrong place for the first 3. The 4th flew off a branch and straight at my head as I raised the camera… I felt the wind as it passed on its way deep into the coppice. I’m not proud of my effort; the fuzzy lemon item beyond the twigs and leaves is a KIWA (you’ll have to take my word for it…).

HAVE ANY BEEN SEEN ON ABACO THIS YEAR?

Last week, Woody took another party to the main hotspot in the Abaco National Park, a protected area at the southern end of the island. The park is huge, covering more than 20,000 acres of (mostly) pine forest. These birds are tiny, about 14 cms long and weighing 14 gms. Despite which they found a female and then a male KIWA in their favoured habitat beyond the pine forest. Those are the only 2 I’ve heard about this winter season.

Kirtland’s Warbler, Abaco Bahamas, 12 April 2018 

WHAT DO I LOOK OUT FOR?

• Gray head with a blueish tinge, gray-brown back
• Yellow throat & underside, with some dark streaking
• Females are paler and more streaked
• Split eye rings – white crescents above and below eyes
• Frequent tail pumping and bobbing (‘tail-wagging’ J. Bond)

WHAT DO THEY SOUND LIKE?

Some would say ‘chip-chip-chip-too-too-weet-weet’. Elsewhere I have found they produce ‘a loud tchip, song an emphatic flip lip lip-lip-lip-tip-tip CHIDIP‘ (Arnott). You be the judge!

 Ross Gallardy / Xeno-Canto

WHAT ARE THE MAIN THREATS TO THE SPECIES?

• Mankind is the primary threat. The breeding areas are particularly vulnerable from deforestation and clearance of the jack pines that are essential for successful nesting and breeding – and therefore the survival of the species.
• Encroachment of development is another threat, as with so many species.
• There is a further threat of nest parasitism by brown-headed cowbirds, to which KIWAs are especially vulnerable.
• In the winter grounds where the habitat is mostly remote or in protected areas, there is rather less of a problem from these factors – for now at least.
• Overall, habitat degradation at one end of the migration – in particular the breeding grounds – poses a serious risk; at both ends, extinction could loom again.

WHO WAS MR KIRTLAND?

Jared P. Kirtland (1793 – 1877) was an Ohio scholar, doctor, judge, politician and amateur naturalist. He was a man of many and varied interests and talents, not-untypical of his time. In the field of natural history, Kirtland’s name lives on in his warbler; and also in a couple of snake species.

The Bahamas Postal Service is commendably active in producing wildlife stamps

Credits: Bruce Hallett (1, 2, 3); Vince Cavalieri (4); Tom Sheley (5); Unattributable (me, in fact) 6; Woody Bracey (7, 9); Tony Hepburn (8); Lionel Levene (10); Birds of North America (range map); Ross Gallardy / Xeno-Canto (audio file); Birdorable (cartoon); BPS (KIWA stamp). Special thanks for all use permissions for images of this rare bird.