It was an amazingly predictable occurrence this Summer. I would be visiting some dense forest patch along one of our creeks and hear or see a Black & White Warbler. Sure, I’ve seen them in summer around Columbus before, but never in the numbers of this year. In June alone I had 10 different sightings. It would seem that Black & White Warblers are rediscovering Columbus after many years of summer rarity. This is not only welcome, but it mirrors the pattern for some other warbler species, suggesting that we should start looking for breeding Black & White warblers here in the future.
For many years Black & Whites were sporadic summer visitors and breeders away from their strongholds down in the forests of southeastern Ohio. I had found single birds in many summers around Columbus, but they were mostly singing males that stayed briefly if at all. Their sites of occurrence varied widely, from the Dublin Scioto river gorge down to isolated woodlots around Rickenbacker airport. Even scarcer were females with young; I had only 4 sightings in 12 years, all at different locations. But last Summer (2012) I had 6 Black & White sightings, a noticeable uptick. Then came this year; by early July, I was actually expecting to find Black & Whites if I visited the right habitat (riparian forests with dense grapevine tangles).
The pattern is neat, but it’s been paralleled by several other birds as well, mostly warblers, but also Summer Tanager and Blue Grosbeak. For years, they would be phantoms, with only a handful of sightings in the Columbus urban area. But then they would have a breakout Summer, and then come to be expected in the right habitats. The poster child for this expansion has probably been the Parula Warbler. When I first moved to Columbus (1994), all you could find for Summering warblers were Common Yellowthroats, Yellow-throated Warblers, and a few Hooded Warblers in large woodlands (like Blendon Woods and Highbanks). Parulas were hanging on only in a few floodplain forests along the Big Darby and further south along the Scioto. But starting in 2002, they began showing up in areas along the southern reaches of the Scioto and Big Walnut Creek, and by 2006 had spread to many creeks around Columbus. Now I can expect to find them along almost any forested rivercourse in Columbus. What changed? The habitat was probably already here, since many of our parks and riverside areas have been preserved long enough to develop a mature riparian forest. It was probably mostly a matter of the birds building up enough population to take advantage of it.
This kind of pattern has been noticed by ornithologists and ecologists before. You need a ‘source’ population that produces lots of young that can emigrate to new areas. For Parulas, it was probably birds along rivers south of Columbus. They had been common in Ross, Pike, and Scioto Counties for many years before their invasion of Columbus. We may be reaching a similar ‘tipping point’ for Black & Whites. They like mature forests with vine tangles, which are common now along Columbus’ rivercourses. They have also had several banner years for breeding in both the Hocking Hills and the forests of southern Ohio. Hopefully, we’ll have them as a regular part of our local summer avifauna in the next few years.