Monday, June 29, 2009

Gray Vireo - A better photograph

Photograph by Mike Stake

Pinyon-Juniper Woodland: Paradise or Purgatory?

Gray Vireo (Vireo vicinior)

“Chu-weet! Che-o! Teedle-e! Chu-u!” The distinct syllables rang out across the pinyon-juniper Woodland (P-J), the song of the Gray Vireo, a New Mexico state-listed as a threatened species. This small, gracefully gray bird has become the New Mexico poster child for one of the most underappreciated but abundant habitats within the state. A recent estimate is that there are 55.6 million acres of pinyon-juniper in the west. It can be rugged country, with steep canyons and hillsides dotted with shrubby trees not much taller than a human. Not much to offer in the way of shade. Often, there’s not much in the way of grasses or shrubs either. Most folks avoid hanging out here. Much of it has been given it over to cows.

More than 70 different bird species breed in the P-J woodland, although you’d be unlikely to see more than 20 to thirty at any one site. These woodlands support the highest proportions of obligate or semi-obligate birds among the forest types in the West. Species that are considered “obligate” are only found nesting in prime habitat condition, birds like the Gray Vireo, which is precisely why there is so much concern about its population trends. Additionally, a high percentage of the total world population of this species breeds in New Mexico, giving our state a high level of responsibility for its well-being.

I’ve been spending a lot of time in P-J country the last couple of years, especially during May and June, when birds are nesting, conducting early morning surveys of all the species present. I’ve grown very fond of this special suite of birds, found nowhere else. The birds of my morning surveys are the very same species that birders worldwide have on their wish list if only they knew where to find them. Actually, it’s not all that hard, once you develop a fondness for all things P-J.

My morning friends range from the spectacularly colored, yellow and black Scott’s Oriole and the laughing call of the Pinyon Jay, to the cute antics of the Juniper Titmouse, all going about their business, just getting by in life. The song of the Black-throated Sparrow greets me at nearly every stop. The Ash-throated Flycatchers are enormously entertaining as they race around chasing each other, oblivious to my presence. The raucous call of the Cassin’s Kingbirds positively make me laugh. And, of course, one could never forget the Northern Mockingbird. He sings the song of all the others, just a few repeats of each and then moves on to another call. He sings all day and all night. If you are camping in P-J country, it seems as if he is singing right into your ear, without pausing for breath, all night long. It was he, along with the pinyon gnats that taught me to sleep in the back of my car. And sometimes, if you are very lucky, you get to hear or see a rarity, like the Gray Vireo.

Mature stands of P-J, with grasses and shrubs in prime condition, and gently sloping hills host the greatest diversity and populations of birds. When there is a nearby water source, the numbers can be simply astounding. One day, I arrived at my designated point to find not one or two, but some 40-50 Pinyon Jays. This site was clearly a Garden of Eden for its residents.

At other location, birds are few and far between, as are the grasses and shrubs. My companions at this site are of the bovine variety, mostly seeking refuge beneath the sparse canopy of the shrubby trees. Water isn’t much in evidence either and the ribs of the cattle show prominently. I wonder how the females will be able to produce enough milk to feed their scrawny offspring. All the emergent edible vegetation seems to have been already eaten. This could be a poster child of another sort, one for poor range management. Most of the birds have flown the coop to better pastures. Even the eagles and hawks are few and far between, for there is little food for their prey, the jackrabbit and cottontail.

We study birds because, much like the canary in the coal mine, they are indicators of biological integrity and ecosystem health and they are quite sensitive to environmental changes. The results of studies like these help land managers, landowners, and others practice best management practices and work toward a system in which multiple uses can co-exist in a beneficial environment.

Our studies have given me the opportunity to really know and understand an unappreciated habitat, and to learn a whole new set of bird songs and habits. It’s a cool place, that P-J, definitely of a different sort! If you’re lucky you might just hear “Chu-weet! Che-o! Teedle-e! Chu-u!”

Wednesday, June 10, 2009

Life as a Little: Hummingbirds

Black-chinned Hummingbird (Archilochus alexandri). Photo by David Powell.

Have you ever wondered what it would be like to be the smallest being in a land of giants? A place where even insects prey on your kind? Welcome to the world of hummingbirds, where reports abound of hummies being snatched in mid-air by the likes of roadrunners, jays, flycatchers, and your favorite pet feline. There’s even a report of a hummingbird snatch by an alert mountain lion in Arizona’s Sonoran Desert Museum. Even the praying mantis, that slow motion insect, sometimes dines on the most diminutive of birds. Lest you wonder if I am filling your head with grisly stories worthy of Snopes, check it out yourself. Just Google “hummingbird eaten by praying mantis” and see what turns up, some 4,130 hits including a YouTube video.

One might wonder just how the little guys are faring since most everything views them as a snack. Not much to worry about here though, because the top predator on the planet has a special fondness for the tiniest of North American birds, but not as a diet supplement. Yes, it is we, the two-legged, land-locked of this planet, that are enmeshed in a love affair with hummingbirds. We watch over, photograph, feed, and protect the little fellows, sometimes to the tune of many thousands of dollars annually per household. Some individuals report usage of up to 50 pounds of sugar a week.

What this means in scientific terms is that the introduction of exotic plants and feeders has produced a widespread energy subsidy that may maintain unnaturally large populations in times of flower scarcity, or when the natural nectar supply is reduced due to drought, insects, or weather. Our stocked feeders have helped increase populations in urban and suburban settings, leading to an overall increase in the species, as evidenced by range expansion and previously unoccupied habitats that are now occupied. Some hummingbirds now overwinter far north of their former range, including a handful that survive Albuquerque winters, almost entirely due to well-maintained feeders.

The two most common nesting hummingbirds in New Mexico are the Black-chinned and Broad-tailed. Both are present in the state, although the Black-chinned is often found at lower elevations, in riparian woodlands. In high quality habitat along rivers, black-chins might be found every 100 meters (33 feet), and this birder can tell you from personal experience that it happens. In the Middle Rio Grande bosque, the Black-chinned Hummingbird is the most common nesting bird, and it’s all-out war as males battle over the rights to sire offspring. Did you know that you actually can distinguish the different hummingbirds by calls?
Surveys here produce not single entries, but 2-3 birds at a time, often locked in combat or issuing battle cries of tiny warriors as they zoom past your head at warp speed.

Hummingbirds have many unique and interesting adaptations too, all necessary for survival. A hummingbird tongue has 2 grooves. Nectar moves through these grooves via capillary actions and the bird squeezes nectar into its mouth when it retracts its tongue. It drinks by extending its the tongue through a nearly closed bill at a rate of about 13-17 licks per second and consumes an average of 1/5 fluid ounce in a single meal. In cold weather, a hummingbird might eat 3 times its weight in food a day, a whopping ½ ounce for a bird that weights 1/10 - 1/5 ounce! However, natural nectar and sugar water alone are not adequate sustenance. Insects comprise a large portion of their diet, and the young are fed insects almost exclusively. Just watch hummies hovering above a slow moving stream. They are hawking insects, the no-see-ums that are a plague on all outdoor-loving people.

Their resting heartbeat is 480 beats and their resting breathing rate is 245 breaths per minute when it is 91 degrees – makes one hyperventilate just thinking about all that hyper-speed. At 55 degrees, their breathing rate increases to 420 breaths per minute! Hummingbirds survive cold nights by going into torpor. This is a state in which the bird’s heartbeat and breathing slow to such a degree that movement is impossible. A torpid hummingbird can be picked up easily, and has no power to move. However, warm it in your hand for just a little while, and the little fellow will spring to life and zoom away.

So for now, in mid-June, we should maintain our feeders by regularly cleaning them with a bleach solution to control mold, mildew, and bacteria. They should be filled with a solution of 1 part sugar to 4 parts water that has been boiled and cooled.

But, soon, probably about July 1, another hummie will arrive, the tiny Rufous Hummingbird, the little red dude. I call him Attila the Hum, for his fearsome guarding of all the hummingbird feeders on your property. He sits in wait for any unsuspecting local species to attempt to drink and then immediately dives upon them to drive them away from ‘his’ feeder. To help reduce the aggression, provide him with one feeder that contains a stronger elixir, a mix of 1 part sugar to 3 parts water. He might just decide to keep that one and leave the other, lesser quality feeders alone.

At any rate, it is important to keep feeders clean and filled until two weeks after your last hummingbird observation of the year and to put them out again in the spring about two weeks before their normal arrival, about April 1 in central New Mexico. You just never know. Perhaps your feeder will be the one that sustains a little throughout the long New Mexico winter.