Sunday, May 31, 2009

Snakes on the Bike

I've been riding mountain bikes in the Boise foothills for 20 years. Each year I see a couple of snakes out on the trail. This year it seems as if I have seen more than all other years combined. I'm not sure if my timing is different, or what the possible explanation might be.
Three Snake Day. Last Tuesday on one 17 mile ride, we found three snakes - one Gopher Snake (Pituophis catenifer), one Racer (Coluber constrictor), and one Western Terrestrial Garter Snake (Thamnophis elegans). Generally the Gopher Snake, which many locally refer to incorrectly as a Bull Snake, is the most commonly seen in the foothills. Yesterday I found another Gopher Snake and saw two other snake trails across the path. Once last year we found that these snakes will hiss loudly when cornered as I stopped just short of running one over.
Rattler! Today we would also find a young Gopher Snake, but the most exciting was the Western Rattlesnake (Crotalus oreganus)! The snake was lying across the trail. I braked so as not to run it over. I originally thought it was a Gopher Snake. The snake was not in a hurry to get out of the way. I ended up stopping right next to it. That's when I noticed the long set of rattles on its tail. He/she was using them and coiling up. It was about 18 inches away! Yikes. I informed the stoker to power away. The snake started making striking motions toward the bike, inches from Karyn's leg. We pulled out of the way and let the people behind know to give the snake a wide berth. Hopefully, he/she made it away from the bustle of the busy trail.
BTW, the Digital Atlas of Idaho provides great reference information for the species of Idaho.

Update 6/3: A reader informed me that the scientific name of the rattlesnake has changed from Crotalus viridis to Crotalus oreganus (see comments).

Friday, May 29, 2009

Owls, Woodpeckers, and other ilk

This week, in my down time between spring semester and the upcoming summer semester, I volunteered to help a graduate student friend of mine with his research. His research is focused on Woodpeckers presence as a predictor for Owl presence within the Boise National Forest. A couple months back I volunteered on the Owl survey portion of the research. This week is the woodpecker portion.
One detail that I wasn't fully up to speed on was that I would be doing fully species surveys and not just woodpecker surveys. Ouch. I had been studying the songs and calls of woodpeckers, but the whole list of species? The day before my departure I spent a good deal of time studying. While my study time was very helpful, it was inadequate for the task of identifying every species.
The work consisted of getting up very early on three mornings and trying to survey as many spots as possible before 11am. The first morning we left from home, but camped the other two evenings close to early survey points.
We surveyed the first two locations together to get a feel for the process. I didn't do too bad with only a few unidentified species. Apparently it was good enough, so I was sent out on my own. The real need is to get the woodpeckers correct and to get the general species richness from the area. That is fairly easy to do, even if you cannot identify every bird. It is always a very educational experience to spend time in the field with a knowledgeable birder and scientist. This trip was no exception. One afternoon we also performed vegetation analysis of one of the points. This was a fairly detailed process taking over 4 hours. Hmm. 90 points, 4 hours each... Micah will be one busy fellow. We also fit in a mountain bike ride! woo hoo! I wasn't a very good guide as I took a wrong turn so we descended a gravel road instead of a cool trail. Anyway, it was fun.
There were a number of special sights in the field:
  • Mating Sandpipers. At my first solo survey location two Spotted Sandpipers mated on a log during my survey.
  • Mating Western Bluebirds. At lunch two Western Bluebirds (life bird for me), landed on a nearby post and mated. Another pair mated next to our camp that evening!
  • Calliope Hummingbird "J" Dance. Our vegetation analysis was disturbed by a male Calliope Hummingbird courting a female. She was perched on a nearby tree. He would fly high in the air, dive down at fully speed and pull up just before hitting the ground. While doing so he would make a snapping sound with his wings at the bottom. This was less that 10 yards away. He repeated the display three or four times. He then hovered in one place, turning 90 degrees every 10 seconds or so. She must not have been impressed as we saw him later perched looking around for her. We would see another "J" dance that evening in camp and another at one of my survey points.
  • Woodpeckers. While none of my survey spots had woodpeckers on the first day, three of my ten spots did on day 2, and three of my nine spots on day 3. Three spots had Hairy Woodpeckers, responding aggressively to played recordings we use during the survey, and one spot had Red-naped Sapsuckers. The other two locations had Northern Flickers. I joined Micah for his last location of day 2. This site produced Red-naped Sapsuckers, Hairy Woodpeckers, and Northern Flickers. Cool.
  • Drumming Grouse. As I mounted my mountain bike at 5:40am on day 3 for the ride to my survey point, I noticed a Ruffed Grouse drumming nearby.
  • Life birds. Spending time with experts always seems to produce more life birds. Mine for this trip - Western Bluebird, White-Breasted Nuthatch, and Cassin's Vireo.
During my summer term I hope to spend a little time volunteering with another friend performing research on American Kestrels. Then there is my own migration research. My field work for that begins July 15th.

Monday, May 25, 2009

Not so Wild in the Wilds

Here is the third and final summary of our continued adventures in Yellowstone. The first part of the story is here - The Tyranny of Nature's Plan, part two is here - The Struggle for Existance.

Our last few days in Yellowstone came with mixed experiences. We had some great wildlife viewing experiences, hiked beautiful trails with little or no people, but mostly dealt with the crowds of people flooding the park. Lesson: Do not spend memorial day in the park! For the first time ever, I was happy to exit the park. Lesson 2: if you are willing to hike more than a mile, there are vast wide open spaces with no one else around. The good news for the wildlife is that most of the people visiting the park are too lazy to get off the road.

Yours truly scouting the local avifauna.

The highlights of our remaining day included numerous views of the druid and cottonwood wolf packs, watching a black bear and her two cubs each evening, and hiking trails and not seeing a soul (until within a mile of the road!).

Druid Pack Wolf on Carcass.
Taking a Bone back to the Den.
Coyote's Turn on Carcass.

"You can't fix stupid". This was a quote from a fellow wolf watcher as we watched two guys park their car in a "no stopping zone" and walk up the hill to get a better photo of wolves. Three yearling wolves had a cow elk surrounded and appeared to be looking for her calf. These idiots walked to within 30-40 yards of the wolves. Some day there will be a wolf/human interaction and it will most likely be the result of stupidity like this. Of course, they will blame the wolf and not the individual making the poor decision. The two pretended to not speak English in poorly phased and poorly accented Spanish. Another reason to avoid the park on Memorial Day weekend.

In another blatant disregard for the wild of wildlife, here is a view of what a badger in a badger den has had to deal with for the past week. These guys are less than 10 yards from the den. Morning to night.

Badger paparazzi.

In all, up to this weekend, it was another fabulous trip to the park.

Moose near Soda Butte.
Savannah Sparrow.

Friday, May 22, 2009

The Struggle for Existance

Here is a summary of our continued adventures in Yellowstone. The first part of the story is here - The Tyranny of Nature's Plan.

The flight of the Eagles. Tuesday evening present a spectacular showing of eagles. Our friends pointed out the Bald Eagle nest where we could see the new hatchlings. Within a one hour period we also witnessed a first year, second year, third year, and adult Bald Eagle flying overhead. Most visited the carcass in the Lamar Valley. These eagles were joined by a juvenile and adult Golden Eagle, numerous Red-tailed Hawks, and the ever present Ravens.

Swim for your life. Wednesday morning after watching the Agate wolf pack, we moved on to watch the Druid wolf pack. The alpha male, another adult, and two yearlings were just leaving yesterday’s carcass. We watched as they made their way up river. At one point the alpha male swam the raging river. The river is high and muddy, with trees floating down. He was swept far down stream. The other adult made it most of the way across before turning back. She just pulled herself out of the river when she was attacked by a lone elk. The elk probably had a calf hidden nearby. The wolf had no fight left and ran from the elk. The two yearlings also tried the river, but turned back as well. They decided to chase a small herd of elk, but they too were too worn to put up a real chase. All three wolves chose to dodge vehicles on the highway instead of taking another turn at the river. An afternoon hike along the rim of the Yellowstone River provided some great bird watching as we looked down on Osprey & White-throated Swifts as Mountain Bluebirds joined us on the ridge.

Yearling wolf splitting an elk herd.


Yearling Wolf from Druid Peak Pack.


Mountain Chickadee with some attitude!

Three’s a crowd. While at Dorothy’s Knoll in the Lamar Valley we looked up to see three wolves marching through the sage brush. Behind them were three coyotes chasing after them. Behind the coyotes was a large grizzly bear! All in the scope at the same time! My read is that the wolves were out on a hunt, the coyotes simply wanted them out of their territory, and the bear wanted to steal anything that the wolves took down. Grizzlies commonly steal carcasses that the wolves kill. As they made their way across the hillside, the bear had to stand up on two feet to see which way the wolves were headed and then run to catch up. He did this three times while we were watching. The last time the bear raised up he turned and ran in the other direction. The coyotes scattered. The wolves were in pursuit of the bear. They chased him up and over the ridge before returning to the valley. The coyotes tried to get the wolves to leave, but they were simply ignored. The wolves bedded down on the hillside and stayed there until dark, and who knows how much longer.

Pika (photo by Karyn).

Bloat and they will come. The action returned to the scene of the dead bison mentioned 5 days ago (in a previous blog post). The bison had died of unknown causes. Her calf stayed with her trying to nurse until finally dying of starvation. We were amazed that no animals had fed on the bison. Apparently coyotes had tried, but could not break open the carcass. That takes a wolf or a bear. After sitting in the sun long enough, it finally attracted the right attention. Apparently wolves were on the carcass last night and a grizzly this morning. We missed that, but got there in time to watch 5 wolves from the Blacktail Pack, including the famous wolf 302, having their fill (previous years blog posts mention wolf 302 and he is featured in a few National Geographic films on wolves). The pack looked thin and rough, they did not appear to be doing well. Later reflection would indicate that these wolves have mange. This puts them and their puppies at risk if they are not well fed. They were joined on the carcass by the ever present Ravens, a Turkey Vulture, Bald Eagles, a Golden Eagle, and some coyotes, but not all at the same time. One bison will feed a lot of mouths and more importantly a lot more puppies and chicks.

Blacktail wolf pack on Bison carcass.

Tuesday, May 19, 2009

The Tyranny of Nature’s Plan

I borrowed the title from one of my favorite lines of a Jakob Dylan song. It’s very appropriate for what you can experience in Yellowstone National Park this time of year. Yellowstone, like no other place nearby, allows nature to play out in front of you. It brings excitement, fascination, life, sorrow, and death. In each of life’s struggles, there are winners and losers. Today’s winner might be tomorrow’s loser.

Finishing up my finals this week, my internal zugenruhe (migratory restlessness) couldn’t wait to get to Yellowstone. We left early Friday morning, but was delayed as I accidently backed into someone in the parking lot. No injuries and only minor damage. It only slowed us up about an hour.

We stopped in to Centennial Marsh on the route. This is a great birding place in South-central Idaho. Lots of water birds here – Ducks , Geese, Shorebirds (Avocets, Stilts, Phalaropes, etc), Sandhill Cranes, and a new life bird for me, a somewhat lost Eastern Kingbird. The Swainson’s Hawks and American Kestrels were also plentiful. From there we headed straight into Yellowstone.

Eastern Kingbird.
Black-necked Stilt.

We had reservations at Madison campground for the first night. We had seen wolves here before, but they are not very predictable. In fact, the wolf’s photo at the top of my blog was taken on a hike from the campground. We wouldn’t see any on this day. We did hear both Coyotes and Great Horned Owls during the night.

The next morning we headed off for the northern range of Yellowstone where most of the wildlife action usually is. Driving by Nymph Lake Karyn noticed an elk standing in the water. This being somewhat rare unless a predator was present, we turned around and found a spot to check it out. The elk was clearly disturbed. Further investigation revealed three wolves on the shore, mostly bedded down. The elk had a significant gash in her front shoulder. The wolves clearly had her before she made it to the water. Now it was simply a stare down. The wolves were in no particular hurry, essentially sleeping on the shore.

After about 30 minutes, the black wolf waded out into the water after the elk. The elk ran into the deeper water where the wolf lost its footing. The wolf turned and the elk attacked chasing him instead. He tucked his tail and lowered his head running until it got on better ground. He then turned and reversed the process. The chase went back and forth six times, the advantage shifting from one to the other. The following highlights some of the sequence.

















In the end, the wolf returned to the shore and bedded down with the other wolves. The elk stayed in the water. We watched for two more hours, the stalement unchanged. It amazes me when you hear the stories of “the wolves decimating the elk”. They always sound so one sided. I have been watching wolves for 10 years and have yet to see a take down. Clearly they kill and eat elk, I have watched them feed on many carcasses, but I have also observed many situations like this one, where the wolves come up empty. Who knows how this one untimely played out, in my opinion it could have gone either way.

Heading toward the Lamar Valley, we found another of nature’s stories being played out. A female bison had died of unknown causes, but apparently not from predators. Her calf, likely only a few weeks old, was trying to nurse. The calf’s fate is sealed, it will die by predation or by starvation sometime in the next day, two at the most. (Update: 3 days later found the calf dead - starvation was the fate).

We decided to camp at Tower campground. It is near the center of the action. Other choices would be Mammoth or Cooke City. Slough Creek campground is our favorite, but it hasn’t been opened yet. Finding our site, we took a hike up behind the campground. We found a number of birds present. The sound of Ruby-crowned Kinglets filled the air. At one point we were staring down a Blue Grouse. He was drumming, it was barely audible as the sound is at the low end of human hearing.

Blue Grouse.

Near the top of the trail we started seeing bones, lots of them. We became much more aware of our surroundings as carcasses are dangerous places to approach. Both wolves and grizzlies will aggressively defend a carcass. No signs of either. But there were lots more bones, too many for a carcass. Then we found skull after skull. It dawned on me that this is likely the dumping ground by the park service for roadkill. We checked it out, but didn’t stay long.

The evening trip into the Lamar Valley would fail to produce wolves. We did get to watch three grizzly bears and took a few good photos as one swam the river, chased some bison, then moved down the valley. The bison mounted a hearty defense, the males grouping up to rush the bear. The bear wouldn’t have a chance to get a calf in this herd. This will be a tough day to beat.

Grizzly Bear.

Before our alarm went off the first two vehicles of wildlife watchers left the campground. We were clearly behind the game. We will have to remedy that tomorrow… We headed into the Lamar Valley in the hopes of seeing the Druid Peak wolf pack. We were not disappointed. One member of the pack was heading down from an apparent carcass toward the parking lot where we were watching from. The den site is on the hill behind the parking lot. Thus, this particular vantage point is fairly popular as most of the to/from trips to the den pass nearby. This wolf passed fairly close, enabling a few great photos.

Druid Peak Wolf.

Later we would see a few other members in the area. The alpha male was found bedded down near a carcass in the middle of Soda Butte Creek. Many of the wolves were visiting the area, but not the carcass itself. That was left to the Common Ravens, Black-billed Magpies, and a Golden Eagle. A number of Grizzly bears were in the area. High on a ridge above the valley was a group of Bighorn Sheep. While there was not the same excitement as yesterday’s exchange, it is amazing to be in one place watching wolves, bears, antelope, bighorns, eagles, etc. The scene also allowed us to catch up with some of our wolf watching friends that we only see in Yellowstone.

Today’s hike took us to Trout Lake and beyond to Shrimp Lake. We didn’t see trout or shrimp! We hoped to see otters, but struck out there as well. The upper lake was still mostly frozen. The lower lake (Trout) was occupied by several pairs of Barrow’s Golden-eye. At one point we heard a woodpecker in the forest. We had to hunt it down to get a positive ID. I am in the process of learning the woodpeckers by sound so that next week I can perform woodpecker surveys for a graduate student friend of mine. This one would be a Hairy Woodpecker. Earlier in the day I properly identified a Red-naped Sapsucker by sound. While watching the Sapsucker we noticed a Mountain Bluebird perched at a nest cavity in an Aspen tree. He flew to a nearby branch. A Northern Flicker jumped in and claimed the cavity. Not sure who it belonged to previously, but it was now in the possession of the Flicker. For a secondary cavity nester like the bluebird, finding a vacant nest is critical. Another of nature’s ways. We wished him luck. A few minutes after our hike we watched a grizzly come out of the trees a couple of hundred yards down the road from where we were just hiking! Hmm.

After lunch it was back to the wolves and grizzlies in the Lamar. Not usually seen mid-day, but today was an exception for both. We would see lots of both. After a few wolves crossed back and forth across the road, apparently shuttling food to the puppies at the den, the photographers decided to line up right at the crossing. Of course, this prevented the wolves from crossing. They tried a number of times to cross, but failed. They eventually circled far around the corner and crossed. From our vantage point we could watch it all. Who knows what the people were thinking. They each had 600mm lens, backing off 100 yards would have provided great shots and not interfered. That evening was beautiful as we watched multiple grizzlies in the Lamar Valley.

Monday produced another beautiful day. The Druid Peak pack were still somewhat visible near their den sight. We moved to Slough Creek, but didn’t see any action. Instead we opted for a morning hike in the marsh. I specifically hoped to see an American Bittern. We were not disappointed. Another new life bird!

American Bitter.

A beaver was working the local ponds, one of the new residents that recolonized after the wolves returned. Lots of ducks, phalaropes, blackbirds, and sparrows filled in the scene. High on the hill above was a pack of wolves, one black and three grey. We watched them mill around the old den site of the Slough Creek wolves. While watching, one elk started walking up the mountain toward them. I couldn’t believe how close she was getting. It was later hypothesized that this elk had a calf hidden in the area. We are just entering calving season. We didn’t observe any direct interaction, now did we see a calf. Another of natures stories that we won’t know the end to. Did the wolves eat or did the calf live…

The afternoon hike took us in search Harlequin Ducks at the confluence of the Lamar and Yellowstone rivers. Once again we were not disappointed.

Harlequin Ducks.

With luck like this, I should definitely set my sight higher.

Tuesday brought many lessons about territory and resources. The morning began watching three separate grizzlies interacting with bison. Apparently those calves look mighty tasty. The bison would have nothing to do with it. Either running away as a heard or chasing the bear as a herd. The herd instinct clearly helps the bison.

High on the ridge we saw the Druid wolf pack. They had come across some coyotes who were causing quite a ruckus. The coyotes had a den in the area. The wolves descended, dug up the den and killed at least 4 pups. There would be no litter this year for these coyotes.

We moved down the valley to Dorothy’s Knoll. Here we found a fresh elk carcass with three coyotes on it. While watching a lone wolf came in and chased the coyotes away. They put up a good fight, but 3 against 1 wasn’t enough. The wolf ate quite a bit before the coyotes returned with reinforcements. This time it was 4 on 1. The wolf could not cover all 4. They grabbed his hind leg numerous times, but if they held on he would have got them. The wolf gave up and moved across the valley. The coyotes returned to the carcass. On the way across the valley the wolf picked up a dead elk calf. He carried it to the river, swam the raging river with the elk calf in his mouth and climbed the mountain beyond. Amazing. By this time one of the Druid wolves found the carcass and fought off the coyotes. He too ate until the coyotes put up another assault to chase him from the carcass. He suffered more damage as he limped away.

Gray wolf (center) surrounded by 4 coyotes.

Later in the day at Floating Island lake we watched as a Barrow’s Goldeneye repetitively attacked another goldeneye couple. Apparently this was his lake and he did not appreciate intruders. He was dive under the water and attack them like a torpedo. Great stuff.

Thursday, May 14, 2009

Weather effects on fall hawk migration

ResearchBlogging.org

I have continued the background discovery process for my research project on songbird and accipiter hawk (hawks that feed on songbirds) migration patterns. A week ago I reviewed a paper on the differential timing of accipiter hawk migration. That particular paper provided a lot to think about and indicated that I may need a more complicated algorithm for my research. This week I found some time to review a paper on weather impacts on hawk migration. I am interested in the research as I will likely need to factor weather patterns as a variable in my analysis.

Kimberly Titus, & James A. Mosher (1982). The Influence of Seasonality and Selected Weather Variables on Autumn Migration of Three Species of Hawks through the Central Appalachians The Wilson Bulletin, 94 (2), 176-184

The paper focuses on the three hawk species migrating through the central Appalachian mountains. Only one of the three species is an accipiter (Sharp-shinned Hawk - Accipiter striatus), while the other two are Buteos (Red-tailed Hawk - Buteo jamaicensis, Broad-winged Hawk - Buteo platypterus), generally not predators of songbirds. The monitoring sites were located in western Maryland, with total migrating birds compared against Hawk Mountain in Pennsylvania. A number of weather variables were used including wind direction, wind speed, horizontal visibility, cloud cover and temperature. The study was conducted over a five year period - 1975-1979.

The paper found that the number one variable in the analysis for predicting migration was the date, followed by the time of day. These were far more significant than any other factors. In other words, when a bird begins a migration, it most likely just copes with the weather conditions as they are dealt. This is not a surprising find in my mind. Further, for the species of my interest, the Sharp-shinned Hawk - A. striatus, they found no significant interaction between wind speed or direction, although a general correlation of good visibility and tail winds was present. The Broad-winged Hawk - B. platypterus, had similar results with a general correlation with good visibility and strong favorable winds. Only the Red-tailed Hawk - B. jamaicensis, produced a significant result. They tended to favor light, opposing winds from the Southeast. These results conflict other findings cited in the paper.

The results seem somewhat logical to me. The Sharp-shinned Hawk spends significantly more time providing its other thrust, than the Buteos which are more dependent upon thermals and gliding. The thermals would be weather dependent, thus you would expect a more significant result for these birds. These results could simplify my work, although they raise more questions than answers. I do not believe this study is sufficient for me to remove weather from my model. I will have to study the other references cited.

Monday, May 11, 2009

Birding with the pros

On Sunday, while I could have been studying for my upcoming exams, I instead went birding with some friends. This was the right choice to make for many reasons. First, I ended up doing well on my exam anyway. Second, birding is just a lot more fun than studying. And lastly, I had an opportunity to go out into the field with some of the most skilled birders around. Not only did I see a lot of birds, over 60 species for the day including 3 life birds, I was able to learn a great deal from my guides. (A life bird refers to the first time you seen a specific bird species in your life).

We started by heading out to Black's Creek Reservoir. This area has been identified by our local Golden Eagle Audubon Society, of which I am a member, an Important Bird Area. On the way we spotted this Burrowing Owl. These are definitely a favorite of mine.

Burrowing Owl.

Arriving at the reservoir, Jay navigated the car through the mud trenches left by other vehicles when the water level was higher. Good news: no pushing this week! Among the sound of gunfire in all directions, official and unofficial shooting ranges nearby, we enjoyed some excellent bird watching. Lots of birds to be expected such as Great Blue Herons, American Avocets, Killdeer, other shorebirds, geese, ducks, and gulls. The highlight was seeing a few new life birds (Least Sandpiper and American Pipit) and getting side by side comparisons of a Least Sandpiper and a Western Sandpiper. I have to admit that I still have some studying to do before I could identify them on my own. From here we moved on to Indian Creek Reservoir.

Indian Creek Reservoir provided much greater diversity for us to see. Maybe because there was no gunfire? Anyway, here we saw a Great Egret:

Great Egret.

Also, Long-billed Dowitchers, Long-billed Curlews, Avocets, Marbled Gowits, all three Teal (Green-winged, Blue-winged, and Cinnamon), a large group of American White Pelicans, Double-crested Cormorants, Wilson's Phalaropes, Western Grebes, etc. The highlight here would be the new life bird - Semipalmated Plover. Once again, we had the opportunity for side by side comparison with a closely related Plover - the Killdeer. I feel more comfortable with my skills on identifying this bird now.

The rest of the evening we spent checking out other areas, looking for sparrows and warblers. We found a number of each. I am very grateful to my guides, Jay and Heidi, who invited me along, shared their knowledge, and were patient with my abilities.

More photos of the trip.



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Saturday, May 09, 2009

Differential Autumn Migration of Accipiter Hawks

ResearchBlogging.org

I have been narrowing in on the specification of my undergraduate research project in Biology/Ecology. The current proposal is related to correlation of migration timing between Predators (Accipiter Hawks) and Prey (Songbirds) at the Idaho Bird Observatory. In the process of refining my research objectives and proposals, I have begun the review of relevant prior research. This is the first paper I have reviewed.

The two most relevant predator species for songbirds are the Sharp-shinned Hawk (SSHA) and the Cooper's Hawk (COHA). The chosen article analyzes the timing of migration between Sharp-shinned Hawks and Cooper's Hawk, differences between male and female migration timing, differences between juveniles and adults, and the differences from year to year.


John DeLong, & Stephen W. Hoffman (1999). Differential Autumn Migration of Sharp-Shinned and Cooper's Hawks in Western North America The Condor, 101 (3), 674-678

Its worth noting that one of the study sites referenced in this paper is likely on the migration flyway south of the Idaho Bird Observatory. Thus, the populations being monitored at that site is likely part of the same migratory population that I will be studying.

The authors reviewed data from two hawk banding sites, one in New Mexico and one in Nevada, over a five year period (1992-1996). They only used banding data due to the unreliable sexing of non-captured birds. Banded birds are captured, where non-captured birds are only observed flying over the monitoring site. Most of the results analyzed are statistically significant, with a couple of non-significant points dealing with the year to year comparisons at one of the monitoring sites.

The authors discovered the general migration order to be juvenile females, juvenile males, adult females, then adult males. The Sharp-shinned Hawks had greater spread in these classes than the Cooper's Hawks. The Sharp-shinned Hawks on average came through the monitoring sites later in the migration season than the Cooper's Hawks.

There are a number of possible explanations for these results provided in the discussion section of the paper. The main question is whether the birds leave their breeding area at the same time. Most likely the juveniles leave early. Whether this is based on their decreasing ability to capture food, or for some other reason is not known. The sex differences could be related to the females leaving the breeding site earlier or the females simply migrating at a faster rate. Since the females are larger than males (reverse sexual dimorphism), they fly faster and have greater endurance. This could be the reason for the differential timing at these southern monitoring stations. It is also possible that the females leave early as their prey base may be less available than the food base for the smaller males. A similar explanation could be used for the differences between the two species. The smaller species (Sharp-shinned Hawk), could be flying slower or could have stayed longer due to different prey base availability. We just don't know. It would be interesting to know if the differential timing is the same at more northern monitoring stations like the Idaho Bird observatory. That could be a whole study in itself.

The results of this paper clearly complicate my potential project. I now must consider the predator species (SSHA or COHA), male/female, and adult/juvenile populations differently. It's definitely a fascinating area of research. I will post additional article reviews as I read them.



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Thursday, May 07, 2009

Dead Week Birding

While all my schoolmates were in class, and my old colegues were at work, I was out birding!! One advantage of taking 4 labs this semester is that during dead week (this week), when most of my labs were done, it seemed like I have nothing to do. There is that research paper due, but I finished it weeks ago. I could start studying for next week's exams, but it just doesn't seem right (actually I did end up studying today). Birding was a much better idea.

Karyn and I headed out to our favorite spot, Hull's Grove. It's our favorite as we can walk from the house. It is about a 4 mile loop from the house, passing two wetland ponds and plenty great bird habitat.

The first stop was the "lower pond". Here we found the usual array of Red-winged Blackbirds, Mallards, an unusual group of Canada Geese, and one of the resident Pied-billed Grebes. There's a pair of Grebes in the pond, so we are hoping for chick photos soon. A narrow trail from here produced many of the day's highlights. A Macgillivray's Warbler, a Yellow Warbler, a Black-headed Grosbeak, and this Calliope Hummingbird. All first for the year!

Calliope Hummingbird.

Hiking past here up onto Chickadee Ridge we could see the Red-tailed Hawk chicks in the nest. There appears to only be two this year. It's possible there was a third one hidden in there. Bank Swallows were flying near our heads. They have definitely moved into the sand cliffs for the year. We stopped at the Cooper's Hawk nest that we discovered a few weeks ago (photos earlier on my blog and here). It looks like incubation is continuing. No sign of chicks at this time. We found the Great Horned Owl family happily in the trees above the "Owl's Roost" trail. Stories about their fledging can be found here and here).

Great Horned Owl chicks and 1 adult.

Great Horned Owl chicks.

We couldn't ignore the song of the House Wrens at the base of the owl tree.

House Wren.

House Wren singing.

Believe it or not, the House Wren is a life bird for me. Woo hoo! Last on the tour of nests was the American Robin nest back near the lower pond.

American Robin nest.

What a great day for a casual outing. One life bird (House Wren), and nine year birds (MacGillivray's Warbler, Yellow Warbler, Bank Swallow, House Wren, Calliope Hummingbird, Lesser Goldfinch, Bullock's Oriole, Black-headed Grosbeak, Lazuli Bunting).



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Sunday, May 03, 2009

Stuck in the mud!

Saturday brought our final field trip for our Ornithology class. The destination was Centennial Marsh in south central Idaho. This is one of my favorite birding locations and is highlighted on the Idaho Birding Trail.

I awoke to the sound of rain, fairly heavy rain for our area. I hoped it wouldn't dampen our prospects too significantly. The group, down a little from our full class, piled into the two vans to head out. The first destination was Indian Creek Reservoir, another location on the Idaho Birding Trail. The road in would prove a little too muddy for the school vans, so we retreated before getting stuck. We moved on toward Mountain Home Reservoir (you guessed it, another Idaho Birding Trail Feature).

The rain decreased to a drizzle as we arrived at the reservoir. There were many shore birds present with a number of new species for my year list. The highlights American Avocet, Yellow-headed Blackbird, Black-necked Stilt, Eared Grebe, Long-billed Curlew, Long-billed Dowitcher, and Western Grebe, among many other less notable species. We loaded up an headed on toward Centennial Marsh

Upon arriving at the Marsh, the access road we planned to use was a little sloppy. We once again retreated. It looked as if the marsh would not be an option for us. There are lots of other wetlands in the area, so all would not be lost. We did find an amazing number of Swainson's Hawks.

Dark morph Swainson's Hawk.

Swainson's Hawk in nest tree.

Another Swainson in another nest tree.

Near one wetland, we discovered just how soft the shoulder of a wet road can be.

Shhh. Don't tell the University!

We scavenged wood from a nearby field and all tried to push, to no avail. We flagged down the first vehicle to drive by. It just happened to be a graduate of the raptor program at Boise State who had taken classes from our professor! What luck. He had a tow rope and pulled us out.

Towing the van.

As if this was not enough of an adventure, I talked the professor into attempting the other access road to the marsh. He agreed to give it a shot.

The second access road was in better condition, so we would get to the marsh after all. The road through provided a number of great species.

Long-billed Curlew

Northern Shovelers(larger) and Cinnamon Teal (smaller).

American Avocet.

American Kestrel eating lunch.

Wilson's Phalarope.

Willet.

Marbled Godwit.

But the adventure was not over yet. I want it noted that my suggestion was to use the other access road to get to the marsh, not to complete the loop. Anyway, the birding just kept getting better and better. On the back side of the marsh, the road was getting sloppier. The lead van made it through ok, but on a short rise, our van could not climb the hill. We were stuck again! Five of us piled out of the van and started to push up the hill. It was very slippery for us to get traction as well. When the van would slide to the side one would go to the side and push it back onto the center of the road. The people in the other van, being a few hundred yards up the road, looked on in amusement. Slowly but surely, we pushed the van over the hump. Clearly we need to be more prepared next time. Maybe take a tow rope, maybe wear better shoes for pushing than Katie was wearing!

Katie's foot!

That would be the end of the major excitement for the day. There were still more bids to see along the way. In all it was a great trip!

Sandhill Crane.


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