Monday, May 30, 2011

Dark Female

If you have seen the movie 'Pale Male', about the light colored Red-tail that was the first of his kind to breed in New York's Central Park, you have an idea of what I mean if I say that our raptor here is exactly the opposite of that hawk: our Red-tail is very dark, very unused to humans, and lives under extremely harsh conditions. For all I know, she may be female. But she also seems to be a pioneer, just like Pale Male.

Around our house we have a breeding pair of American Kestrels, a group of Harris Hawks, many Cooper's Hawks, a hunting Peregrine Falcon, a visiting Prairie Falcon, and a wintering silver gray Northern Harrier. They share the habitat with formidable and dangerous competition: there's always a pair of Great Horned Owls around. And there is neither water and nor a supply of feral pigeons.
There are Red-tail nests along the Santa Cruz River and in lusher parts of Saguaro National Park, and the hawks come through our part of the desert regularly, but I've never seen the aerial shows of mating pairs here.

The first indication that  Red-tails were moving in was an abandoned nest in a saguaro with no sign that it was ever occupied. We checked ever now and then, but nothing changed: no fresh twigs, no whitewash....

Only once in late January I caught a glimpse of a pair of Red-tails on the power line at the far side of the 400-acre state land.

 Then a dark silhouette appeared a couple of times high above us while we were walking our dogs. When the tail caught the sunlight it flashed in striking, bright orange contrast to the clear blue desert sky. But nothing ever happened at the old nest. The bird seemed protective of the area though, and we mostly stayed away.

On this fresh cool morning (after a spell of near 100 degrees) we were going to give our dogs a special treat - a long walk through the state land. No hawks in the sky yet. The dogs watched Zebra-tail Lizards scramble out from under a thin cover of sand and scurry away, dug feverishly for squirrels, looked longingly for traces of cattle ....We passed the empty old nest, picked up some trash, collected some nice rocks, and inadvertently stepped over a rattler who completely ignored two shoes and eight paws coming within inches of his low-profile coil.

When I looked up, Randy was standing next to a saguaro, and right over his head the shape of two or three small hawks in a big nest were outlined and back-lit by the rising sun. They stood completely still, and so did we. Two of the nearly grown chicks had  light chest feathers. Harris Hawk or Red-tail? We memorized the location and rushed home to get cameras and our friend Frank who wouldn't want to miss this.

 Returning a little later we were discovered by the dark hawk. She circled. Banked right above our heads. Screamed at us. She is definitely not used to people walking her territory, and let us know her displeasure long before we came close to the nest.

Staying at a fair distance, equipped with very long lenses, we walked in a wide circle to get the sun behind us. The nest is on the west side of the Saguaro, nestled in its massive arms. Until noon no possible angle would allow a clear view of the inhabitants without looking into the sun. I wonder why it's so exposed to the afternoon sun, the hottest around here. The wind blew sharply out of the west all day yesterday, as it often does. But the other, unused, nest has the same orientation.

 While we were there, the chicks never moved. They are tall and leggy and already have lost all of their downy  fluffiness. One is as dark as the parent, one has a light chest - did I only imagine a third one earlier?

 While  female hawks stay with the nest and the young while the chicks are small, leaving all the hunting to the male, both parents would be hunting to provide enough for the hungry beaks of chicks this big. I'm worried because there was only a single parent around. The urgent calls should have alerted the other partner. Shortly, the hawk was joined by another big soaring shape, but that one turned out to be a Turkey Vulture. Still no sign of another adult hawk, but time for us to leave them in peace.

Saturday, May 28, 2011

Sabino Canyon at the end of May

So far this year we were spoiled by rather low temperatures during the days and nice chilly desert nights. But now it's definitely getting too hot for hiking in the lower desert. On Saturday we will supposedly reach the first three digit temperatures. But I had  postponed my last Sabino trip for the season several times, and I really wanted to go.

Racoons at Sabino, Watercolor from 1992

During my first years in Tucson (when I lived on the east side of town on River Road) I used to run in Sabino Canyon nearly every evening, and I never went home without seeing something exciting like several Black-tailed Rattlesnakes, a Tarantula Hawk with his prey, Mule Deer watching me, Mountain Lions imagined (I always just missed the big cats lounging around the visitor center). On the evening a friend proposed to me we saw Fire Flies which are rare out here, and a cute family of Hooded Skunks which are not. Racoons washed crayfish at the creek and bats were clicking over head.

But those were the hours after sunset. Last Thursday I arrived at 10 am. All other visitors seemed to stay close to the visitor center, even the trams were going mostly empty. Two young Roadrunners, maybe too tame for their own good, were hanging out at the tram stop, rushing from shade to shade, making their sharp noises that seem to be as much a clapping of their pointed beak as they are vocal. I kept checking the white balance and the color saturation on my camera. But it was the blistering sunlight that bleached all colors into monochromes.
Even Quail and White-winged doves seemed subdued by the heat. Fewer Lizards than usual, and I saw no snakes, even though I even crawled into the cool moist hollow of the first bridge were the road crosses the  dried up creek. Wild Cotton was blooming there, very ethereal with its translucent white petals and only a few leaves, but standing taller than I.

I had hoped to photograph interesting wasps on blooming  mesquites, but the catkins were far past their prime and many had long green beans sprouting from between the last flowers. Mesquite bug nymphs were clustered around those beans, already big and beautiful in the 4th and 5th instar of their development. I collected a few because Carl Olson had told me that the UAICollection could use some more.

 Staring up into the trees, I found that there were other gleaners at work, though after smaller insect prey than I. Amazingly bright Yellow Warblers, a pair of Black-tailed Gnat-catchers feeding a single chick.

 Verdins were still working on a nest. A lone Black-throated sparrow was scratching under Palo Verde and Prickly Pear, and since I was standing quite still, he came within a few feet and to be captured on video and still photo. These sparrows are so elegant, and usually quite shy.

Even in the steeper parts of the trail a Zebra-tail and a Greater Ear-less (this must be the narrow zone where their habitats overlap) are the only lizards that I saw, but I believe that I heard the rustling of a heavier Spiny Lizard (most likely Clark's) on the rough Cottonwood bark. By now I was too exhausted to find out.

At the dam, there was only the sad and muddy rest of an evaporating puddle. Even the Predatory Waterbeetles and Giant Waterbugs had left. I the moist sand I found Aztec Pygmy Grasshoppers.

Dozens of tiny, extremely quick Carabids were racing for cover. Measuring only 3 to 4 mm and dark, they were difficult to photograph even in the studio, but I captured a couple anyway.

A Spot-winged Glider, Pantala hymenaea landed on a bush - that's a new Dragonfly for me! It was cooler among the big Willows and Ashes, so I felt invigorated enough to follow a Midas Fly to get a picture hopefully good enough to identify it.

Under the tall trees of the riparian forest where several Hummingbird feeders are part of study on bird migration, Broadbill males were living up to their reputation as feisty warriors.

 Loud hammering drew me to a mostly dead tree in time to film a Ladder-backed Woodpecker's successful grub hunt. He devoured one and carried the next one away to his brood and  left me to wonder which beautiful buprestid beetles that might have been...

 Time to leave the riparian area and cross the mile or so of open desert under the relentless afternoon sun. There are water stations in Sabino Canyon, so I was only carrying a tiny bottle that I refilled four times, but I was also dragging two cameras around with me - the heavy SLR for reliably good macros and the little point and shoot, that is excellent but sometimes doesn't focus, to take videos and long distance shots of birds.

A Round-tailed Groundsquirrel escaped from the heat of the desert surface into the canopy of a mesquite tree enjoying the added bonus of fresh mesquite beans.
Luckily, my car was parked in the shade of that same tree.

Tuesday, May 24, 2011

Night Hawks

 Two dry washes cut through our land and continue through the State Trust-land to the north. Before our rodeo loving neighbor started to run his roping cattle there, we walked our dogs nearly every morning along those arroyos. Even though they haven't had much running water in years due to drought and earth-moving activity in the nearby quarry, they are lined with trees. The tallest blue Palo Verdes and the widest Foothill Palo Verdes grow there.

Ancient Ironwoods still bear the scars from the time when wood was cut  to make charcoal for limestone kilns that have long since disappeared. Even dead Ironwoods seem to last for ever. We use one grotesquely crippled one for orientation and call him Hieronimus after the Dutch painter of medieval horror visions.

Strange big-headed birds sleep motionless during the heat of the day in those strangely shaped trees. They melt into the shape of a branch with bark-colored feathers and by sitting along its direction rather than crosswise. Only when the dogs are running right underneath its hide-out, a bird flies up. Soundlessly like an owl, but gliding like a big slow swallow, zigzagging  close to the ground and never in a straight, predictable line the Night Hawk swoops away.

White markings close to the tip of the long pointed wings flash identify him as a Lesser rather than a Common Night Hawk. The bird lands on another low strung branch nearby and becomes invisible again. To photograph, I have to follow, but more often then not I loose the bird, until a dog accidentally flushes it again or maybe another one.

 In the last hours before sunset the birds change from shapeless lumps into elegant long-winged, aerial acrobats with the shape of a small falcon but a much slower wing beat..
Night Hawk headed southeast in the evening light. In the back Wasson's Peak, Tucson Mts.
During the dry months of May and June the insectivorous predators have to undertake a daily journey from our arroyos on the west side of the Tucson Mountains to the Santa Cruz River about 10 miles to the north.
There they feed on dancing swarms of gnats and mosquitoes but also catch large moths. Their short, enormously wide beaks are surrounded by bristles that allow them to scoop up prey while erratically swooping close to the ground and over the water.

Can you find all 7 Night Hawks?
 I was at the river at the Sanders Road Bridge in Marana yesterday. There must have been close to fifty Night Haws gliding right towards me  through gaps in the vegetation, low over the river, high in the velvety evening sky, holding their pointed wings in a slight v-shape, tipping from side to side, seeming to do acrobatic tricks. In the setting sun they kept changing from dark silhouettes to glowing beacons when they turned, their white wing bars flashing. They were  competing for insects with kingbirds and other flycatchers, several species of swallows and White-throated Swifts.

Lesser Night Hawks over Sweetwater Wetlands, Tucson, in May 2014, Photo by Chris Rohrer
 As the evening progressed, the other birds disappeared, leaving the air over the river to night hawks and bats.

During the monsoon months the night hawks will stay closer to our house, feasting on swarms of termites and ants that, during their nuptial flights,  rise from the desert sand like smoke. On those evenings we will also hear the strange goat like sound produced by air rushing through the tail feathers of the night hawks during the aerial dives that are part of their mating display. This sound together  with their low to the ground flight gave their European relatives the reputation to swoop down on goats to steel milk -  hence the German name 'Ziegen Melker"

Friday, May 20, 2011

The Secret of the Moon Flower

Sacred Datura III watercolor by Margrethe Brummermann

 Datura wrightii is blooming again on the sandy banks along the Santa Cruz River and Sabino Creek:  Thornapple, Jimsonweed, Moon Flower, Tolguacha, Sacred Datura - this perennial herb in the Nightshade family is appreciated by many but also abhorred  by a few.

Plagiometriona clavata
Although it's protected by powerful alkaloids (atropine, hyoscyamine and scopolamine), there are several Leaf Beetles that regularly feed on its leaves. The Tortoise Beetle Plagiometriona clavata can be found in July, and two year-round regulars are in the genus  Lema:

Leaf Beetle on Solanaceae - Lema trabeata - male - female
Lema trabeata
Lema daturaphila. The name means 'Datura loving'

Trichobaris compacta
Of the three weevil species that live and breed exclusively on Datura, two Thrichobaris species are 'leaf notchers' that betray their presence through punctures all over the leaves, but the third species utilizes the flowers and I have yet to find it.

The Manduca caterpillar or hornworm loads up on alkaloids wherever he finds nightshade plants. In our area he would have to find somebody's  tomato patch to match the juicy Datura leaves.

  Leafhoppers, Antianthe expansa and their nymphs suck sugar water from the phloem of the Datura stems.

Sacred Datura IV, Watercolor by M. Brummermann

The tightly rolled Datura flowers unfurl before dawn. The huge delicate funnels seem to be illuminated from within. In our climate, they only last til the late morning.

Georgia O'Keefe found eroticism in those deep trumpet shapes. Shamans and  teenagers have been seeking hallucinations from the plant. Witches used it in love potions. Insects find protection from predators with the help of the plant alkaloids that they ingest. Some art show visitors have asked me with astonishment why I would paint such a poisonous weed that also has an unpleasant smell. I was told that it's illegal to grow it in Arizona (luckily, nature doesn't care)
Besides its beauty, I admire the staying power of the Datura. It's a leafy, lush, delicate plant, completely exposed to evaporation and wind damage in our desert environment. Only its fruit, the thorn apples, seem to fit in where almost all vegetation is leathery, succulent, and covered in spines and thorns.

Of course, the Datura prefers to be close to water or else dies back completely during the dry season (9 months out of 12 it seems lately) Only the root stays alive. I once saw an over ten feet long Datura root system exposed in the wall of Antelope Canyon, one of our beautiful, treacherous slot canyons.

For me, the Datura flower holds another mystery. When I point my camera into the flower to shoot tiny White-masked Bees of the genus Hylaeus, I often notice a lump obstructing the depth of the white throat. Checking flower after flower, I find it in nearly all of them, even in the wilted ones that are more than a day old. At closer investigation the lump turns out to be a pretty substantial beetle..

The only way to get to it is to rip the flower lengthwise. I find a sleeping scarab wedged deeply inside. 

Elytra and actually the whole back-end are a dark cream color, the pronotum is a rich brown, and the head, which is the body part stuck most deeply in the flower, is shiny black. That's also in the name of this scarab: Cyclocephala melanocephala (black-headed round -head). 

It's in the Subfamily Dynastinae, which makes her (I only found females) a cousin of Hercules and Rhinoceros Beetles. 

For night active scarabs, these guys are surprisingly alert. When the flower is forced open, the beetles immediately start walking away and even buzzing off in a short, tumbling flight. Did I mention that I stopped by the river on a cool morning on my way to work?
This ectotherm beetle seems more active than it should be, given the outside temperature. 

Once I get to the entomology department (only a little late) I ask Carl Olson directly and Bill Warner by email if they know why the beetles are in the flowers? Carl speculates that the flowers open right when the night-active beetles seek shelter and offer a nice bright landing platform to an insect that is always attracted to lights. He adds: "..and it might be warm in there?"
Bill Warner soon emails back: "Cyclocephala melanocephala is known from Datura flowers; it frequents other types of flowers (I think including ariods) in the tropics.  There are some papers about Cyclocephala and flowers--some species are primary pollinators and some aroids "heat up" their flowers specifically for Cyclocephala." (Aroideae are Jack in the pulpit type flowers).

So is it an example of coevolution between the beetle and the plant?
There seem to be a number of advantages for the beetle.
The majority of night active scarabs flies during humid, warm monsoon nights. But in May, C. melanocephala will often experiences temperatures in the low sixties and even fifties, so a warm hiding place would be an attraction. (Elevated Floral CO2 levels, indicating elevated respiratory activity and thermogenesis were found in Datura Flowers).
The beetle fits snugly into the long throat of the flower and is not only hidden from predators but also engulfed in the peculiar smell of the chemical defenses of its host. The beetles hind-end matches very well the creamy white of an aging Datura blossom, a likely adaptation to this preferred hiding spot. The dark head and pronotum always face into the depth of flower.

I don't yet understand whether there is an equal advantage for the plant that would justify the cost of extra metabolic heat production. Some researchers assume that the elevated CO2 levels serve as a signal to the primary pollinator, Manduca sexta, Our beetle with its smooth surfaces seems indeed an unlikely pollinator. When crawling into its hiding place, the beetle passes the reproductive organs of its host flower, but it wouldn't be useful to transfer pollen between individuals because it seems to stay in just one flower for the day. So what am I missing? I'll have to ask some more experts....If I find out more, I'll add it here. 

Datura II, Watercolor by M. Brummermann

Context- and scale-dependent effects of floral CO2 on nectar foraging by Manduca sexta  Joaquín Goyret, Poppy M. Markwell, Robert A. Raguso PNAS March 25, 2008 vol. 105 no. 12 4565-4570 
The Role of Thermogenesis in the Pollination Biology of the Amazon Waterlily Victoria amazonica
ROGER S. SEYMOUR* and PHILIP G. D. MATTHEWS, Ann Bot. 2006 December; 98(6): 1129–1135.