Saturday, April 27, 2013

Avian Infanticide

On April 24th, the turkey vultures in Missouri laid their first egg. The egg was captured by video-maker Priscillash and celebrated by cam watchers. We were all perplexed when the egg disappeared. What happened to it? A quick review of footage revealed the culprit - a male turkey vulture. He spent roughly 20 minutes rolling, banging, scraping, rubbing, and biting the egg on and off camera view. The barn's owner was not able to find the egg or eggshells, so we assume the vulture consumed the egg after cracking it.

This behavior appears to be infanticide. Although we haven't seen it at the nests we watch, it is not an uncommon behavior in birds. Avian infanticide may involve killing eggs or hatched offspring. It includes:
  • Exploiting young as food
  • Sexually-selected or paternity-influenced infanticide
  • Resource competition
  • Social pathology, gender selection, reproductive fitness
We've seen falcons and eagles exploit dead young as food, although we haven't seen them kill young for food - the difference between infanticide and cannibalism. In the case of the bald eagles at Fort St. Vrain, and the falcon Belinda at the Allen S. King plant, the dead young were readily available and the live young needed feeding. Although it seems awful to many human watchers, exploiting dead young as a resource very probably saved live young, especially at Fort St. Vrain, where the eagles were struggling with cold weather and a heavy snow fall that reduced food availability.

The vulture destroys the egg
The turkey vulture may have been committing sexually selected or paternity-influenced infanticide. He - we think it was a male given the brow ridge - could have destroyed the egg because it was not his egg. There is some very lively discussion going on about whether or not this male was last year's father. If he was, he may have destroyed the egg because it wasn't his egg. In this scenario, he arrived at the barn to find his mate had already paired with another male and laid an egg. Since the egg wasn't his egg, he destroyed it. If it wasn't the same male, he may have driven off the original male. Once again, since the egg wasn't his egg, he destroyed it.

In this scenario, paternity was uncertain. The male bird was assuring that all of the offspring produced in the barn would be his. The female could most likely still be fertilized if the egg was destroyed, given that she hadn't laid all of her eggs yet. We haven't seen re-clutching in the presence of eggs, but we have when failed eggs have been removed from the nest. By eating the egg, the male effectively removed it.

Infanticide can also be compelled by resource competition. In this scenario, a parent does not have enough food or nest space for all of its young.  It may kill weaker young or refuse to feed or incubate them. Although Cain and Abel syndrome occurs between offspring instead of adult-to-offspring, it is an example of resource competition that can result in death. As cruel as it seems, the young best able to adapt to limited resources are the ones who will survive.

Finally, we have the last trio: social pathology, gender selection, and reproductive fitness. Social pathology occurs when infanticide occurs for no discernible reason.  Social pathology is a highly maladaptive behavior that doesn't benefit the individual or group. While I have tried to avoid using loaded terms, the closest human analogy would be murder. Eclectus parrots practice infanticide based on sex: that is, mothers kill male offspring. And some birds appear to practice brood reduction to maximize reproductive success, killing particular offspring while leaving others that are presumably more fit. Less mouths are easier to feed. We talk about the role that natural and sexual selection play in driving specialization. Could infanticide also be playing a role?

While this behavior is very difficult for us to understand, it is part of what birds do. The social and emotional lives of birds are complex, and it is my feeling - and I stress feeling here - that birds and humans have some states that are analogous to one another, and others that are not. We shouldn't judge the birds for living their lives - this is not a part of bird life we've seen very often, but it is still a part of bird life. We'll keep watching the barn.

Things that helped me write about this topic:

Friday, April 26, 2013

Red-Tailed Hawks, Nest Greenery, and Ants

First Meal
The hatchling red-tailed hawk at Eaglecrest ate its first meal yesterday afternoon. Like bald eagles, red-tailed hawks eat an extraordinary variety of prey. I thought I detected some fur on baby's first meal, but red-tailed hawks also eat birds, reptiles, insects, fish, and carrion. Eaglecrest's wonderful wildlife resources will provide plenty of food for the rapidly growing hawks.

We also saw the hatchling nibbling at the green leaves lining the bottom and sides of the nest bowl. Watchers know that Stitch and Spot regularly replenish the sprigs of small leaves placed haphazardly around the nest. As pretty as it looks, the hawks aren't bringing in greenery for decoration. The aromatic blue oak leaves may mark active territory, discourage parasitic insects such as fleas, ticks, fly maggots, and lice, or perform both functions at the same time.

Repelling Insects
We know that blue oak leaves release a wide variety of volatile organic compounds. A number of them have been identified as possible insect repellents, including isoprene, an oil that reduces thermal stress and repels insects. At least two mechanisms have been suggested for isoprene's repellent properties:
  • Number one: Isoprene hides host plants and animals by interfering with an insect's ability to smell a host. Parasites can't locate hosts hidden in an isoprene haze.
  • Number two: Isoprene repels insects. As the isoprene outgasses from the freshly cut leaves, it ozidizes to terpene, an insecticide. Many insects actively avoid terpene.
Whatever the mechanism, a number of animal species use greenery in and around their nests, burrows, and dens, including twenty-six members of the order falconiformes. Many of them choose highly aromatic leaves and/or bark, suggesting that appearance or appetite alone do not account for the regular delivery of fresh greenery to their homes. We've watched birds go to amazing lengths to build nests and protect their young. Why wouldn't they try to repel parasites and insects? 

Having said that, the leaves don't appear to work on ants. We periodically witnessed ants on and around the nest on April 25, although they didn't appear to be unduly disturbing the hawks. I'm no ant expert, but they appeared fairly small to me. Ants both migrate and swarm, so while may have been attracted to the nest by prey leavings, they also may have been simply passing through. I haven't been able to find much evidence that ants are especially harmful to birds, outside of a few highly specialized species. Some birds even allow themselves to become covered with ants - a practice known as anting that may be yet another defense against parasites. 

Enjoy watching the wildlife at Eaglecrest!

There is some debate about whether or not birds use greenery to repel or reduce parasites. Although I found the evidence to be pretty compelling, a few writers and researchers listed other possibilities, including that hawks are programmed to snip greenery in much the same way they are programmed to build nests, that hawks like greenery in the nest, and that the greenery is the result of hawks snipping branches away to improve sight lines in the nest.

Things that helped me write about this topic:

Thursday, April 25, 2013

Hatch at EagleCrest

We have the first hatch for Stitch and Spot Sr. at Eaglecrest. Here's a video thanks to mochamama22. A few special moments from the video:

  • 4:38: Stitch's 'funny' feather
  • 6:54: Stitch bites the eggshell
  • 7:04: Dad visits the nest
  • 7:07: We see the hatchling 
  • 7:44: Mom covers the hatchling

Follw this link to watch the hawks:

Monday, April 22, 2013

Raising Mabuhay

Mabuhay is a two month-old Philippine Eagle produced at the Philippine Eagle Center near Davao City. He represents the second generation of Philippine Eagles to be produced here: his father, Pag-asa, was the first Philippine eagle ever produced in captivity. Little Mabuhay is number twenty-five. Mabuhay is a Tagalog word that means 'live', 'cheers' or 'welcome'.

In the video below, Philippine Eagle Foundation staff are feeding Mabuhay with a puppet that resembles an adult eagle. This will keep Mabuhay from imprinting on his keepers, which would make him non-releasable in the wild. Imprinting occurs during a period of time early in an animal's life, when it forms attachments and develops a self-identity. The puppet will help assure that Mabuhay imprints on Philippine eagles, not human beings. This is important, since birds imprinted on humans will seek them later in life as sexual and social partners. Properly imprinted, Mabuhay will seek other Philippine eagles.

The Philippine eagle lives in forests on eastern Luzon, Samar, Leyte, and Mindanao. The world's longest bird of prey, it weighs 10 to 18 pounds and measures 2.8 to 3.3 feet in length. It has a dark face, a large bluish-grey beak, blue-grey eyes, and a distinctive nape of trailing light-brown feathers. Adults have dark brown backs with white underparts.

The Philippine eagle is so large that I thought it would spend most of its flight time soaring. While it does soar, it is also amazingly maneuverable for such a large bird. It twists, turns, and folds its wings as it flies through the forest pursuing bats, deer, lemurs, monkeys, birds, flying foxes, giant cloud rats, and snakes and lizards. While the Philippine eagle would be a formidable hunter no matter where it lived, the lack of large predators in its range makes it the dominant hunter in the Philippine forests.  Unsurprisingly, each breeding pair requires a very large home range to successfully raise a chick. A study on Mindanao Island found the nearest distance between breeding pairs to be about 8.1 miles on average, resulting in a circular plot of 51 square miles.

The Philippine Eagle is critically endangered. Only 180 to 500 are believed to survive in the wild in the Philippines. They are threatened primarily by deforestation through logging and expanding agriculture. The Raptor Resource Project has partnered with the Philippine Eagle Foundation to help them save the Philippine eagle through captive breeding and habitat conservation.

Preserving habitat takes money. Today, on Earth Day, we are asking our supporters to make a donation to the Philippine Eagle Foundation to help purchase rainforest habitat in the Philippines for this highly endangered bird. A few dedicated people snowballed into a widespread effort to bring back the Peregrine falcon and Bald eagle in the United States and Canada. We can do the same in the Philippines for the Philippine eagle. To donate to the Philippine Eagle Foundation, please click the button below:

To learn more about the Philippine Eagle Foundation, follow this link:
To learn more about little Mabuhay, follow this link: A Chick At Last

Friday, April 19, 2013

What Makes Birds Incubate?

Red-tailed hawk Stitch incubating eggs
Looking out my window this morning, it seems unlikely that spring will ever arrive. But most of the birds we watch are incubating eggs or, in the case of bald eagles, feeding young. Clearly, they aren't waiting for the ice and snow to melt.

Daylight length has a profound effect on the physiology of birds. As the length of daylight increases, light receptors deep in the brains of birds detect the changing day length and trigger the seasonal development of the reproductive system. Hormones flow and reproductive organs increase in size. Courtship begins and pair-bonds are formed or re-established between male and female birds. Nest work kicks into overdrive: eagles and hawks fetch in sticks and greenery, while falcons create a scape, digging into gravel or substrate with their breast and pushing with their legs to create a depression for the eggs.

So what makes active birds like hawks, falcons, and eagles spend so much time sitting on eggs? Like the rest of bird reproductive behavior, egg-sitting is triggered by hormones. Initially, luteinizing hormones trigger the production of testosterone in males and progesterone in females. Testosterone triggers sexual behavior and aggression in male birds, while progesterone induces egg production in female birds. Birds are really louder and brighter in the spring, when bird song, plumage, and courting behavior are in full swing. However, shortly before incubation, female birds (and male birds that share incubation duties) experience another big hormonal change. Prolactin, a hormone which promotes incubation in birds, rises sharply while other hormones decrease. Opioid peptides stimulate prolactin secretion, which may explain why even active birds become lethargic while incubating their eggs.

The eagles have young and Stitch and Spot's eggs are ready to hatch. Over the next 30-40 days, the peregrine falcons will enter what Bob calls the incubation doldrums. We'll watch them sit, and fritter with gravel, and sit, and sit some more. The induced lethargy will end quickly once eggs begin hatching, and prolactin (and presumably opioid peptides) begin declining.

Prolactin plays an interesting role in bird parenting behavior. We'll return to it a little later in the season. See the bottom of the page for my links.

This chart shows the relationship between testosterone and prolactin in a male emu. Note the sharpness of the curves.

Things that helped me learn and write about this subject:

Thursday, April 18, 2013

Peregrine Survey

Young falcons at Aggie's Bluff in 2012
According to the weather forecast, 4/16/13 was the only sunny day this week. Time for a peregrine survey! Dave Kester and I set off at 6:30 AM for the Lansing Power plant cliff, where we quickly located two adult falcons.  One was sitting on a cliff nest box that we mounted several years ago to attract falcons away from a ledge that provided poor shelter and was accessible to raccoon. The ledge nest site failed to produce young, but the nest box has proven productive. Nine young have fledged from this site since 2009.

We were very pleased to find an adult female falcon on Guider’s Bluff just south of the town of Lansing, IA.  We heard one bird wailing, indicating that there was probably a second falcon on site.

We did not find any falcons on Aggie's Bluff, two miles upstream of the Lansing, IA bridge.  We decided to head upstream and return to this cliff later in the day.
We found two adult falcons at the Shellhorn cliff just south of Brownsville, MN.
We did not stop for long at the new V cliff south of Homer, MN, since I had confirmed two falcons defending the site on my last river survey.  I remember hovering over this cliff ten or more years ago in a Bell Jet Ranger helicopter and thinking that someday this cliff could attract falcons, since it looks much more falcon-friendly from the air than from the ground.
Dan Berger at Homer Bluff. Dan documented
the extirpation of the Peregrine from the Mississippi
in the 1950s. He is still banding birds today. 
We were very excited to find two falcons defending the Homer/P4 cliff that has not attracted nesting falcons for a few years.  We observed one falcon fly and land in a tree very close to the eyrie location.
We have falcons at Red Wing Grain, but needed to confirm whether we also had them at Diamond Bluff, in Diamond Bluff Wisconsin. We were pleased to find two adult falcons defending this cliff, but we don't know whether they are using a nestbox or a pothole. This cliff will need some observation. We mounted this nest box over 20 years ago, and we are very pleased with how it has held up.

We saw falcons at West Bluff and Maiden Rock, staying at Maiden long enough to confirm one falcon protesting a vulture flying to close to the eyrie. All appears well at this location!

There were no falcons at Twin Bluff in Nelson Wisconsin. This is our third visit to this cliff without finding falcons, although we found two adults on our first survey. A mystery.
We found one falcon on the cliff face at Maassen's bluff, and our friends who live down below indicate that all is well.  The pair is using an eyrie we improved by adding 80 pounds of pea-gravel to improve nest drainage.

I observed one falcon at Castle Rock on 4/9/13, during driving rain.  On this visit, we observed two adult falcons. However, the adult female left the cliff and flew out of sight, heading directly north. She did not return. The adult male set off in the direction of the Bay State Milling plant in Winona, MN, where our nestbox camera has confirmed four eggs.  If I recall correctly, every time we have falcons at Bay State Milling we do not have nesting falcons at the nearby Castle Rock cliff.
We passed by the Homer/P4 cliff again and made our way downstream to a new cliff.  The light was very poor, since we had to look into the setting sun, but we did spot one falcon perched on a limb near the cliff top. We raced back up to the Homer (P4) cliff hoping to confirm falcons were not just bouncing back and forth between the two cliffs.  We were pleased to find two adult falcons on site.
 By this time it was getting late in the afternoon, and we wanted to return to Aggie’s Bluff to see if a second visit would lead to finding a falcon. Despite the poor lighting conditions, we were pleased to find one falcon perched on the cliff face.
We returned home at 6PM, pleased to finding so many falcons defending Mississippi cliffs.  It was not that many years ago that some thought we would never have the peregrine back on these historic cliffs. It is wonderful to see them back 30 years after my first captive bred falcon was released in the river valley.
Bob Anderson

Sunday, April 14, 2013

Meet Stitch the Red-tailed Hawk

Eaglecrest begins hatch watch for Red-tailed Hawk 'Stitch' and her eggs on April 17th. Stitch is a buteo, a genus of birds of prey noted for broad wings, sturdy builds, and soaring flights. Her eggs are estimated to begin hatching on April 19th. To watch Stitch, visit Eaglecrest's Ustream site:

Once her eggs hatch, Stitch will provide most of the brooding while mate Spot provides the family with food. Red-tailed hawks eat a wide variety of live prey, including mice, gophers, voles, chipmunks, squirrels, shrews, bats, quail, corvid birds, reptiles, and even insects and earthworms. Although Red-tailed hawks have been observed eating carrion, they prefer live prey.

Life in the nest will follow a familiar pattern for altricial birds. When the nestlings are small, Mom Stitch will spend a lot of time brooding and tearing food for them. As they become able to thermoregulate, the young hawks will be less interested in brooding and more interested in exploring the nest. Developmental stages include standing, food tearing, playing and interaction, and wingercizing.  The young hawks will fledge beginning at roughly 42 days of age. They will begin to catch their own prey six to seven weeks after fledging and will become independent of their parents at about four months of age. Since Red-tailed hawks tend to return to breed in the area they were born or hatched, it is likely that Spot and Stitch's progeny will settle nearby. Spot and Stitch's linage may have occupied Eaglecrest for a very long time. Although they weren't modern Red-tailed hawks, the fossil record shows that Accipitrine hawks had evolved by the beginning of the Pleistocene epoch. Some of those fossils were found at the La Brea tar pits, roughly 250 miles away from Eaglecrest.

We might enjoy watching Red-tailed hawks now, but for much of the past century, they were a maligned bird. In 1932, Dr. Thomas S. Roberts wrote:

"Thirty-four of the forty-eight states have laws that variously discriminate between the beneficial and supposedly harmful species of Hawks and Owls and make provision for the former group. Potection, however, was removed from all species in 1925...Since that time, a general and wholesale slaughter of these birds has been going on...Both Hawks and Owls are so greatly reduced in numbers as nesting birds that they have become somewhat of a rarity."

As has been noted elsewhere, the Red-tailed hawk made a spectacular comeback from the dark days of bounty hunting and shoot on sight. Now protected by the Migratory Bird Treaty Act, the bird is a very common sight along open fields and roads, where it hunts for small rodents. The Red-tailed hawk comes in a variety of sizes and plumage colors and patterns, but all adult Red-tailed hawks are easily identifiable by their bright red tails, which molts out in the hawk's second year of life.

What's happening in the eggs right now? Probably something like this:

RTH eggs are lightly-speckled to whitish ovals. Take a look at this video for a peek at the eggs, which can be seen at 8:29 into the video:

We are looking forward to hatch!

Things that helped me learn and write about this topic:

Thursday, April 11, 2013

Where Did That Falcon Come From?

Screen shot of the online banding info database
Yesterday, facebook user Jeff Suggs asked if any of the falcons we watch have Australian roots. The short answer is 'No'. As far as we know, none of the falcons we watch can trace their ancestry back to falcons imported from Australia for North American captive breeding and release programs. Having said that, the Peregrine Fund did include Australian Falcons (Falco peregrinus macropus) in the breeding stock they used to produce falcons for release.

To quote Captive Breeding and Releases of Peregrines (Falco peregrinus) in North America:

"Breeding projects were stocked with birds from many locations. The CWS Wainwright facility had birds taken from the wild as nestlings from northern and southern Alberta, the Yukon, and the Northwest Territories, Canada; the McGill facility had birds from northern Quebec. The Peregrine Fund at Cornell University had birds taken as nestlings from Alaska, Scotland, Australia and other places, while the Fort Collins facility had mainly birds from the Rocky Mountain region. Most of the birds at the SCPBRG were from California."

From what I was able to find, most of those falcons were released in the eastern United States. The use of non-native stock was quite controversial, as chronicled in the wonderful book Peregrine Falcon: Stories of the Blue Meanie by Jim Enderson.

So how do we find out where birds come from? I like to use the online Midwest Peregrine Falcon Database, which is maintained by the Midwest Peregrine Society and the Raptor Center at the University of Minnesota. Take 11/X, the immature female at Great River Energy. To look up her band number, follow the link below and enter 11/X in the number field of the color band info category. If you have a band color, select it from the dropdown to narrow your search. Most of our birds are either black over green or black over red.

The Midwest Peregrine Falcon Database:

It turns out that 11/X is MaryEllen, a 2012 hatch from Queen's Bluff in Winona County, Minnesota. Since both of her parents are known, I can trace her ancestry through them. MaryEllen's mother has FWS band number 1807-77654. By entering that number into the FWS field, I learn that her name was Jean. Jean was produced at Maiden Rock in 2001, the first year there were birds on that cliff, and banded by Bob.Jean's mother was the unnamed 1807-61966, who was produced at Firstar Bank in Cedar Rapids, Iowa, in 1999. Her mother 1807-29469 was captively produced by breeder and falconer Pete Widener and hacked from Des Moines Iowa in 1991.

Now for the Dads. MaryEllen's father was Cranberry 816-38602, produced at the Dairyland Power Alma plant in 2004. Bob also banded this bird. I remember it well, since we had to rush up the stack in between thunderstorms to get the young falcons. His father 2206-62744 was produced at Firstar Bank in Cedar Rapids, Iowa in 2000. His father 2206-13875 was produced by breeder and falconer Bruce Haak, a friend of Bob's, and also hacked from Des Moines, Iowa, in 1991. MaryEllen's parents are related through grandfather 2206-13875, who was present at Cedar Rapids in 1999 and 2000.

Thanks to bands and bird banders, the North American peregrine falcon is probably the most-documented bird population in the world. As I said in another post, if you see a band number, please post it here or on our forum. We love to know who we are watching!

To learn more about banding, follow these links:

Jean's mate Gunnar was a bird produced and released by the Raptor Resource Project at Effigy Mounds in 1999. We'll be writing more about that project later this year. 

Wednesday, April 10, 2013

Peregrine Falcon Nest Box Program

Bob and falcon at Minnesota Power, Cohasset plant. 
Several of the Peregrines we watch are nesting at utilities, including Xcel Energy's Sherco, Blackdog, King, Prairie Island, and Monticello plants; Dairyland Power's Alma and Genoa plants, Minnesota Power and Light's Cohasset and Hibbard plants, Great River Energy's Elk River plant, and Alliant Energy's Cassville and Lansing plants. Our utility partners are also home to other birds, including bald eagles (Xcel Fort St. Vrain), great horned owls (Xcel Valmont), kestrels (Xcel Pawnee), and blue herons (Xcel Riverside). This isn't an accident - utilities provide an excellent home for peregrine falcons and other species of birds. A list of the sites we watch online can be found at

The Raptor Resource Project started working with utilities in 1990, when peregrine falcon Mae was spotted at the Allen S. King plant in Oak Park Heights, Minnesota. A falconer and plant employee named Paul Simonette called Bob, who verified the sighting and asked for permission to construct and mount a nest box on a catwalk at the 400' level of the plant's stack. The site was tall, near water, inaccessible to most predators, and accessible to humans while remote from their daily activities. It was perfect!

At that time, the peregrine falcon was still highly endangered. Mae's mother MF-1 was produced by the Raptor Resource Project and released from the top of the MultiFoods building in Minneapolis in 1986. When she returned to breed in 1987, she became the first Peregrine to breed in the wild mid-continent, in the US or Canada, since the species' extirpation in the early 1960s. Mae, who hatched in 1989, was one of just 13 wild peregrines produced mid-continent that year. An awful lot of falcons have hatched since then. Here is a look at total numbers as of 2012 from the nine utility/industrial sites we watch online:

  • Xcel Allen S. King plant. First year: 1990. Total young produced: 60
  • Xcel Sherco. First year: 1992. Total young produced: 54
  • Minnesota Power and Light, Cohasset. First year: 1993. Total young produced: 59
  • Xcel Blackdog. First year: 1993. Total young produced: 56
  • Dairyland Power Alma. First year: 1997. Total young produced: 55
  • Dairyland Power Genoa. First year: 1998. Total young produced: 46
  • Red Wing Grain. First year: 2001. Total young produced: 27
  • Great River Energy. First year: 2007. Total young produced: 19
  • Minnesota Power and Light, Hibbard. First year: 2008. Total young produced: 10

Xcel Energy could have said 'No'. While having a peregrine falcon on site was really cool, it was also a risk.  The company had no responsibility to provide a home for endangered species, and suppose Mae died? Any persons who bring danger or death to an endangered species can be fined up to $100,000, and the story would have been headline news. But plant manager Mike Miser said 'Yes' - he thought the peregrines were neat, plant staff were enthusiastic, and the birds provided wonderful organic pigeon control. The Utility-Peregrine Project was underway!

After the success of the Allen S. King plant, several other utilities expressed an interest in their own peregrine falcons. In addition to expanding the program at Xcel Energy, we received requests for nest boxes and or releases from Dairyland Power, Minnesota Power and Light, Wisconsin Power and Light (now Alliant Energy), MidAmerican Energy, Rochester Gas and Electric, and many more. Cargill, Red Wing Grain, and Bunge America also joined our efforts, installing nest boxes in Lake City, Minnesota, Red Wing, Minnesota, and McGregor, Iowa. A few statistics:
  • The utility peregrine program has produced over 1000 young falcons in the wild. 
  • At present, birds are nesting at 17 RRP/utility sites. Species include peregrine falcons, bald eagles, kestrels, great horned owls, and blue herons. An osprey pole had to be removed for bridge construction in Stillwater, Minnesota, so we are waiting to see if ospreys adopt their new pole at the Allen S. King plant. 
  • I pulled a list of 473 peregrines known to have survived into adulthood. 64 of them fledged from utilities and went on to nest at other utilities, bluffs, grain elevators, bridges, and buildings.
  • Peregrines have been nesting at our oldest site, the Allen S. King plant, for 23 years. 60 falcons have been produced here alone.
  • Our birdcam work began in 1998, with "Mae's Internest". The cam was a sensation, and Xcel Energy's site was briefly the world's busiest corporate website according to
Our work with utility companies is sometimes controversial. Power lines present electrocution and collision hazards and the impact of wind turbines remains unknown. Utilities in general are not considered especially friendly to conservation. But the Utility Peregrine Program, a unique marriage of bird conservation and power production, was crucial to recovering the peregrine falcon, delisted from the Federal Endangered Species List in 1999. We've also worked with power companies on avian utility interaction issues and would like to think that our falcons are one of the reasons Xcel Energy voluntarily signed a Memorandum of Agreement with the Fish and Wildlife Service in 2002. Our partnership with utility companies has greatly benefited birds. 

Monday, April 08, 2013

Tess, the Count, and Larry the Lizard: Adventures in Symbiosis

Eaglecrest watchers might be familiar with Larry the Lizard, who periodically appears at the mouth of the Barn Owl nest, sunning and catching insects. I'm no lizard expert, but I think 'he' - we don't actually know the gender - might be a northwestern fence lizard. Larry resembles a northwestern fence lizard, lives in fence lizard range, and acts like a fence lizard.

Observers have noticed that Larry and the owls appear to have a symbiotic relationship. While barn owls prefer rodents, they will eat reptiles. However, they don't bother Larry. Is it because he eats ants and other bothersome bugs before they enter the nest? As David McDonald, Eaglecrest's owner, put it, "They look at him, but they don't bother him. He keeps ants and other bugs out of their nest."

Symbiosis has not been documented between northwestern fence lizards and barn owls, but it is known to occur between screech owls and blind snakes in the southwestern United States. Screech owls bring blind snakes - a sightless underground insect hunter that looks somewhat like a long earthworm - into their burrows, where they eat the pests that compete with nestlings for stored owl prey, as well as ants and other insects that could harm the young birds. Some people believe that the owls intentionally use the snakes as nest maids, while others believe that the snakes are dropped during the parent-chick handoff and simply find the burrow a good place to live. Fred Gehlbach, a biologist from Baylor University in Texas, found that snake-occupied screech owl nests produce more and healthier fledglings than do snake-free nests. Once the owl family leaves, the snake crawls down the tree and returns to its underground home. According to Gelbach, blind snakes are common guests of at least four owl species. The snakes we've seen slipping in and out of the nest at Eaglecrest might be performing a similar function.

So it seems at least possible that Larry and the snakes are engaged in a mutually symbiotic relationship with the owls - a relationship between individuals of different species that benefits both. The ants and other pests attracted to the nest's prey remains provide Larry with a steady diet, while the owls reap the benefits of built-in pest control. The snakes may be performing a similar function inside the owls' burrow. As scary as snakes might look to some of us (human) watchers, it is quite possible that they and the lizards are welcome guests.

Thanks to Eaglecrest for giving us a look at Larry!

Symbiosis may be much more common than we think. It comes in a number of different flavors, including:
  • Mutualism:  a relationship between individuals of different species that benefits both.
  • Commensalism: a relationship between individuals of different species in which one species benefits and the other is neither harmed nor helped.
  • Parasitism: a relationship between individuals of different species in which one species benefits and the other is harmed.
We've seen all three of these at the Decorah Bald Eagle nest. I'll return to this subject in a later post. 

Things that helped me learn about this topic: