Showing posts from July, 2020

The Phainopepla is a curious bird

The Phainopepla is a curious bird. Their tall crest and feathers of silky black or gray are accentuated by piercing blood-red eyes. They reveal luminous white wing patches in their somewhat slow yet buoyant flight. In the Sonoran Desert they fiercely defend their clumps of desert mistletoe from intruders with an inquisitive “Wert?” A charming and charismatic bird at first glance, the closer one looks into any aspect of its natural history, one realizes the veracity of Allan Philips' claim in The Birds of Arizona: "Phainopeplas have no respect for the rules."

"And there isn't any need for you to doubt it"
-Rum Tum Tugger
Phainopepla nitens – sketch by the author

"Wert?" call

The Phainopepla song is a modest volume series of burry and polyphonic phrases, evocative of blackbird and shrike vocalizations in their complexity. Those that work closely with Phainopepla have noted a bizarre vocal behavior when they're distressed while being handled: they unleash a near constant stream of loud (and very convincing) imitations. These include a variety of hawk and other predator calls, perhaps in an attempt to distract or frighten, but they also mimic a wide variety of small harmless songbirds. Investigating this behavior, there is a study that shows a variety of imitations mixed with alarm calls is most effective at rallying other nearby species to help mob a predator. When threatened, the Phainopepla vocally simulates a multi-species scolding mob attempting to drive a predator away. This in turn helps manifest a real mob with real birds. Avian aural Twitter bots.

Under normal circumstances one rarely hears these imitations in the field though. I had no idea Phainopeplas were mimics at all when I encountered a lone male singing from the top of a palo verde in the Phoenix Mountains Preserve in January 2019. I could hear the louder burry phrases typical of their song but interspersed throughout were quiet sounds I couldn’t quite make out. I snuck myself under the tree where the bird was singing and with the assistance of my microphone I then could hear what he was muttering.  Listen below:

After some introductory phrases he launches into a series of imitations at around 17 seconds in what is referred to as their Quiet Song. In this two minute clip I hear imitations of at least a dozen species, from desert dwelling critters like Curve-billed Thrasher and Harris’ Antelope Squirrel to a variety of higher elevation forest birds like Spotted Towhee, Cassin’s Kingbird, Tree Swallow, and Western Wood-pewee. Unlike the famous mimic, the Northern Mockingbird, which belts out its collection of imitations at the top of its lungs, the Phainopepla whispers them. They can’t be heard from more than a stone’s throw away, so who are they for? Sometimes quiet songs serve to strengthen pair bonds when birds are in close proximity – but I didn't see any other Phainopeplas nearby. Was he practicing?  I doubt it – they sound pretty crystallized to me. When listening to the extended recording he uses the same imitations many times with very similar phrasing and delivery. Was he feeling threatened, either by me or something else? Again, I doubt it – giving quiet imitations of birds that are currently hundreds of miles away doesn't seem like an effective mob-eliciting strategy in this context. Whatever the case may be, the function or meaning of imitation seems to be flexible in different contexts. They are very impressive though, why be so coy about it?

"And there isn't any need for me to shout it"
-Rum Tum Tugger

Wait a minute, how is this desert-breeder imitating so many forest birds to begin with? Without doing any research we’re already clued-in to a fascinating aspect of this bird’s natural history just by listening to his peculiar quiet song. Clearly, this male has been around. He has seen (and heard) some things.

While Phainopepla are fiercely territorial, mistletoe berry-loving, desert-breeding birds in winter and early spring, they largely vacate the premises by early summer. Around the same time, they are found in mid-elevation riparian and oak woodland habitat, sometimes hundreds of miles away. There they are social creatures, forming loose colonies, nesting together in the same trees, eating berries from the same bushes. They incorporate many more insects into their diet. They’re like a different bird.

For almost a century people have wondered whether these were distinct populations of Phainopepla or the same birds breeding twice a year in different habitats. There are still many details to be worked out but a recent study has shown GPS-tagged desert-breeding Phainopepla do migrate to the expected higher elevation habitats each year and there is no discernible genetic difference between populations in each location. This strongly suggests the same birds breed in both habitats. Aside from a handful of very interesting outliers, most other North American birds are constrained by various environmental, physiological, and behavioral limitations and only have one chance per year to breed. If Phainopeplas are in fact itinerant or migratory double-breeders, “[They] would be behaviorally flexible –in migration, breeding, and social-structure– to a degree not documented in any other North American bird” (Chu, M. and G. Walseberg, Birds of the World, 2020). As for the rules and constructs, generalizations and metaphorical boxes we try to fit birds into, the Phainopepla indeed has no respect for them.

“For he will do as he do do
And there's no doing anything about it”
-Rum Tum Tugger

Roseate Burrow #18

In the Summer of 2019 I worked on Stratton Island in Maine for National Audubon's Project Puffin. There were no puffins but many birds bred on the island including four species of tern. While Common Terns were the most...common, there was a sizeable Roseate population in the center of the colony, a few Arctic Terns scattered throughout, and Least Terns on the sandy beach landing.

We had many intimate and intense interactions with the terns that summer. We regularly checked nests, counted eggs, weighed, measured and banded chicks all while the adult terns screamed in our ears, pecked the tops of our heads with surprising force, and aggressively covered us with tern excrement.

Typical tern greetings in slow motion

It wasn’t all chaos though. We also spent a lot of time in platform blinds throughout the colony which allowed us to observe the birds in relative peace. Courtship dances, copulation, eggs hatching, chicks hopping up and down awkwardly flapping their wings. We watched certain chicks get fed over and over while others starved. We watched curious birds wander too far from their nest only to get pecked viciously by their neighbors. We also watched many birds take to the sky on fresh wings, over time gaining the grace and buoyancy of their parent's flight.  The blinds allowed us to observe the entire breeding process in all its messiness.

A view from the blind

The blinds were still a bit removed though. Towering several feet over the colony, we watched through binoculars and spotting scopes. With nearly four thousand terns before eggs even started to hatch, the sound of the colony was, in a word, extra. Any attempt to hear one specific bird was masked by the sounds of hundreds of other vociferous squawkers. What we couldn’t hear were the quiet tern sounds – not necessarily an oxymoron.

Partway through the season we were visited by Bob McGuire (a world class sound recordist, just check many of the audio credits on the Sibley Birds app), who helped open my eyes to the magic of remote recording or "drop rigs." One morning at camp he excitedly passed around his headphones for us to listen to what he had just recorded. The concept was simple enough, he had hidden small omnidirectional microphones in the rock burrow of a Roseate Tern then watched from a distance. When we slipped on the headphones we heard the terns like we never had before.

Omnidirectional mics have several benefits: They’re small and hideable, have low self-noise, and are less susceptible to wind noise. However they have one drawback for isolated species recordings: omnidirectional mics record in all directions equally so the passing lobster boat or obnoxious bird or any other noise will be picked up as if the microphone is pointed directly towards it. What I hadn’t considered was the inverse-square relationship between distance and intensity of sound: if you half the distance between a mic and a sound source, the intensity of sound will be four times greater. The trick is getting the mic close enough to the subject.

The next evening I tried it out myself:

(Headphones Recommended) -- Recorded with Zoom H5 and FEL Clippy XLR EM172s

The recording starts with the sound of a typical alarmed tern colony. Common and Roseate Terns yell in the distance and then return to their nests all riled up. It is past sunset, fiery clouds fading into the dark blue night. We hear the parent Roseate Tern return, giving its piercing alarm call and aggressive chatter just outside the rock burrow, making sure neighbors keep their appropriate distance. Switching to the more social "chevink" call at 1:03, it heads into the burrow. Moving from left to right in the stereo field, the adult is greeted by its 3-5 day old chicks with quiet scratchy calls. After the initial excitement they all quietly mutter to each other. When I hear this I imagine the adult tern settling down as the chicks huddle and squeeze underneath to rest in the warmth of their parent’s puffed out body feathers. All is calm in burrow #18. Neighboring terns also quiet down and we hear the distant rhythmic crashing of ocean waves. Of course, it never fully settles for long – tern colonies are only varying levels of raucous at all hours and trouble is never too far off.

This is likely the first of many posts about the sounds of Stratton Island and is just one of many examples of this recording technique. Normally field recording attempts to capture and recreate what we can hear, but remote "drop rig" recording can allow us to hear what we otherwise couldn't. Paradoxically, the technology that removes us can also embed us more deeply with our subject, allowing a peek into intimate social interactions with the emotional salience afforded by sound. We hear what birds whisper when we're not around.

Disclaimer: I was trained and permitted to work with these birds and their safety and well-being was always my top priority. One should not approach nests if doing so would cause undue stress or have an adverse effect on nesting success. It is illegal and morally reprehensible to disrupt the nesting of birds for any reason.