A Birder’s Tale: Spotting A Tricky Rare Hybrid, The “Lawrence’s” Warbler

 

PROLOGUE

Why a prologue? Because birding backstories are almost as fun as the birding itself!

The birding network is so broad and keenly in tune that sighting reports move lightening fast, at least when they travel through the usual channels (e.g, birding listserv). But sometimes reports creep up where you least expect them. On Saturday night, my husband and I went downtown to a fundraiser inside the old stone mill that houses a swank restaurant and art gallery.

The mill was the last place I expected to get the skinny on local birds. In fact, in the midst of so many non-birders I had to work hard to have “normal” conversations about school principals, stimulus packages, and county taxes. Lord, have mercy…

I walked up to the piano player, a friend of ours who was nursing a brew after his last set. Steve is a Harvard-trained naturalist/educator who lives with his family on a 200-acre nature preserve he purchased from the heirs of Joe Taylor, founder of the American Birding Association. He, his wife, four children, and 71 barn animals cohabitate on this marvelous piece of property where Roger Tory Peterson once slept.

The point to all this is that Steve leads a colorful life, and has more stories than you can shake a stick at. This night, he unfolded a yarn about the Great Peacock Getaway that occurred three nights earlier. Somehow, one of his wily peacocks had popped the lock on his barn door and ventured forth toward bluer skies and greener acres. Its motley crew of peahens followed suit.  The peahens eventually returned but the lone male, which apparently has big cajunas, was still at-large. The neighborhood hotline indicated the bird was last seen strutting in an easterly direction. “Towards India,” Steve supposed.

Or possibly New Hampshire. Steve was largely unfazed by his peacock’s independence as he hearkened the mantra, “Live Free or Die.” 

So I invited myself to bird on his property the next day, and in this context he mentions that he’d been leading a nature walk for the Mendon Foundation earlier that morning at Rush Oak Openings, a 228-acre nature preserve in the Town of Rush in southern Monroe County (New York). And, by the way, the participants caught great looks at a “LAWRENCE’S” WARBLER and a SNOWY OWL.

Um, say what?

At this point, it is beyond me why we spent twenty minutes prattling on about peacocks when Steve was sitting on the location of a Snowy Owl PLUS a rare warbler. See, Steve is a good birder, but removed enough from the obsession that it doesn’t interfere with “regular talk.” If you’re reading this post, you probably wish you were so lucky.

Either that, or you are wondering why I’m prattling on about Steve’s peacocks when there’s a rare hybrid to report.

Now you know how I felt. Okay, okay, I’m getting there…

WORD OF THE RARITY 

News that a SNOWY OWL and a RARE HYBRID WARBLER were seen that morning just a few miles from my home made my eyebrows pop over the rim of my glasses. I demanded every detail Steve could muster. 

The SNOWY OWL was seen on a utility pole near the road, looking like he was on the move. This makes perfect sense so I didn’t hold my breath to see it the next day. But I still don’t have Snowy on my year list, and this will be the SECOND individual I’ve missed in my hometown in the space of five months. UGH!

A “LAWRENCE’S” WARBLER was seen near the main entrance near the field’s edge. It was easy to find and everyone in his group laid eyes on it.

This was all I needed to know. I ran home to study up on the “Lawrence’s,” which is part of what is known as the Vermivora Complex of hybridizing warblers.

THE VERMIVORA COMPLEX

Hybridization of Golden-winged x Blue-winged warblers occurs wherever their ranges overlap. Hybrids paired with either species produce a variety of backcrosses. 

The “Lawrence’s” warbler is a specific backcross that shows recessive traits including the black throat patch and wide ear patch of the Golden-winged, with the yellowish underparts and two white-wing bars of the Blue-winged. 

Ornithologists believe that a “Lawrence’s” Warbler is created when a first-generation hybrid Golden-winged x Blue-winged (which is called “Brewster’s”) pairs with either another Brewster’s (Bonter and Lovette, Living Bird Vol. 26-2) or either full species (Sibley, 2000). 

The song of  Blue-winged is a lazy beee-buzzzz. The Golden-winged sounds like a buzzy bee, bzz bzz bzz. Hybrids may sound like either parent, or sing an odd combination of both songs.

Though there is regional variability, hybrids make up an average of 5% of singing males (Gill, et al. 2001). The “Lawrence’s” phenotype is the rarest form, and is expected to appear in about 1 of every 16 progeny of a pair of hybrids (J. Confer, NY 2008 Breeding Bird Atlas). 

In New York, Golden-winged (G-W) populations are trending downward (they are a Species of Special Concern) while Blue-wingeds (B-W) are gaining ground. 

Ornithologists speculate that hybridization could be a major force in the eventual extirpation of Golden-wingeds, for two reasons. First, it seems that B-W genes more easily flow into birds with G-W phenotype. Second, G-W warblers pair with hybrids more often and produce more hybrid young than B-W warblers (Confer, et al. 2003).

To put it another way, it appears genes of the Golden-winged Warblers are slowly becoming ‘washed out’ by those of the Blue-winged. But research on the population genetics of the Vermivora complex is ongoing and many questions remain unanswered.

What’s important to remember is that “Lawrence’s” Warblers:

• are not a distinct species, but part of a hybrid complex
• are rare, making up a tiny fraction of Vermivora hybrids, which themselves average only 5% of singing males
• have an olive back and yellow head
• have a black throat patch and a wide black ear patch 
• have yellow underbelly and two white wing bars
• can sing either the Blue-winged or the Golden-winged song, or a peculiar combination of both
• are beautiful to look at!

SPOTTING THE “LAWRENCE’S” WARBLER

The next morning I popped up out of bed before sunrise, brewed some coffee, polished my lens, studied Peterson & Sibley one more time, and dragged my mostly willing husband out of the house by 7 am. 

Spring birding doesn’t get much better. The weather was clear and sunny. Bird songs filtered from every corner of the preserve. Light was in our favor as we traversed in a south-southwest direction with the morning sun at our backs. We quickly tallied up several vocal migrants:

• BLUE-GRAY GNATCATCHER
• HOODED WARBLER
• COMMON YELLOW THROAT
• YELLOW WARBLER
• WOOD THRUSHES
• FIELD SPARROW
• SONG SPARROW
• CHIPPING SPARROW
• WHITE-THROATED SPARROW
• EASTERN TOWHEE
• BALTIMORE ORIOLE
• AMERICAN GOLDFINCH
• HOUSE FINCH
• BROWN-HEADED COWBIRD
• BLUE JAY
• NORTHERN CARDINAL

Hark! Is that a Blue-winged I hear?

We took off in the direction of the bee buzzz and heard more than one male singing from the other side of a wide hedge row. After a few minutes of assessing the situation, it seemed unlikely that the birds would pop over to our side, so I walked ahead looking for a pass-through amongst the shrubs. Paul hung back and hoped one would pop over to our side.

Just ahead, my eye caught movement at eye level. I had to pass up great looks of an Eastern Towhee scratching the leaves in order to follow the warbler-looking bird flitting in the shrub.

It was hard to focus because the bird kept moving away along the edge of the hedgerow. It only wanted to show me its rump, but when I finally caught a glimpse of two white wing bars and a yellowish tinge underneath, I got excited. If only he’d show me his face…

Then Paul, who was about 25 yards back, whispered a loud, “Hey!” Turning away from what could be the “Lawrence’s” seemed foolish, so I pointed into the brush and put my finger up as if to say “Wait a minute.”

Paul was clearly unsatisfied with my response, and made an even louder “Tshht!” followed by a whistle to grab my attention. I looked back to see him frenetically waving me over, like “What’s are you DOING? I’ve got something!” And he looked up the path at me, frenetically pointing into the bush, like “Dude, leave me alone!  I’ve got something!”  This was marital birding at its finest.

I finally view a glimpse of the bird in my bins; its all-white throat and yellow spectacles revealed it to be NOT a “Lawrence’s,” but a White-eyed Vireo….so I hoofed it back over to Paul.

Sure enough, he has the bird, the “Lawrence’s” Warbler, spotted in a tree about 30 feet high. The Blue-winged-sounding bird eventually DID peek over the hedgerow and when it did, it landed close-by, then whizzed past his head so close he had to duck! It landed behind him in a small shrub only ten feet away. Paul had had amazing looks for a fraction of a second before it flew up again to the tree that was now in our lenses.

I whipped out my camera and for the next ten minutes, the bird flitted from station to station around us in this magnificent old field.  Eventually, it landed on a limb in good light and let me take these photos: 

 

 

Full species or not, this was a spectacular-looking and very cooperative bird. Knowing that it is a rare form made it all the more exciting. 

We eventually tore ourselves away from the “Lawrence’s” and continued birding. We traced another beee-buzzz to this Blue-winged Warbler, which gave us the confidence of a decent comparison:

 

Soon after, the harsh croaks of a Ring-necked Pheasant rang out over the marshy creek eight, maybe nine times. No sign of the bird, however, which made us wonder if it was a hunter calling in game? This place is known for illegal shooting, so maybe we were almost the game!

While crouching in what I hope wasn’t pheasant-like posture, we heard a gentle bee, bzz bzz bzz from deep in the marsh. 

On any other day, I would have called this a Golden-winged Warbler, but today had emphasized the importance of not making assumptions in the field. Was it another “Lawrence’s?” Could there be two in one area?  My husband swears he had two in his sites back in the field. The NY Breeding Bird Atlas says that Golden-winged Warblers are known to breed in swamp forests, so maybe we DID have a bona fide Golden-winged? The secrets, I’m afraid, are buried in the marsh at Rush Oak, and e’er will be.

And so ended our day of birding. Am happy to report that we did not mistake any windblown white shopping bags flapping in a tree for a SNOWY OWL. And that by posting the sighting to the listserv a bunch of other folks added “Lawrence’s” Warbler to their NY list.

Our Sunday school lessons were:

• If you’re birding an area where Golden-winged and Blue-winged warblers overlap (check your range maps) and hear either’s buzzy song, do not check the species off your list until you see the bird’s field marks.
• If you hear a buzzy song that sounds suspiciously like one or the other, but different, it may be a hybrid. Get a closer look.
• Familiarize yourself with the plumage variations shown by hybrids so you can more confidently ID them in the field.

 

Good Birding!

 

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