Archive for June, 2014

This week I began my summer field season. I am planning weekly excursions up into, and throughout, the Sierra Nevada mountains to find Evening Grosbeaks, my study species. My first day in the field was a modest start. I left West Sacramento at 3:00am and drove up highway CA-49 to the San Francisco State Field Campus just outside of the tiny town of Bassetts, CA. When I arrived, at around 6:00, it was lightly misty and on the cold side. I walked around the field camp a little and heard the forest wake up. It was not long before I heard my first Evening Grosbeak of the day and setup my equipment. As the weather cleared, I got some work done testing how Evening Grosbeaks respond to recordings of various kinds, but there were not that many grosbeaks around. There were a bunch of other birds around that gave me some great looks, including several near collisions. At various points in the morning, I was nearly hit in the head by a Western Tanager, a Red-breasted Sapsucker, a White-headed Woodpecker, and a Mountain Chickadee! I also got to see an Osprey circling high overhead with its breakfast, a moderate sized fish, in its talons. But, since the grosbeaks were not especially cooperative I decided to try a new spot. I continued east on CA-49 to Yuba Pass where I was happy to find more grosbeaks along with a few Red Crossbills, lots of Cassin’s Finches, and several Chipping Sparrows, one of which landed on the side of the road not five feet from me and sang and sang. Delightful! After a while, and grosbeaks only showing up few and far between, I headed back down towards Bassetts where I saw Townsend’s Solitaire, which were a real treat for me, and a very lovely pair of Fox Sparrows. Then, after a brief stop in at the Sierra Skies RV Park in Sierra City, I was homeward bound. Odd as it sounds, the RV park in Sierra City was a great field site for me during my Master’s work. All in all, it was great to get out into the field and shake the dust off my methodology. I only got 5 actual trials, and since I am aiming for 10 each day, that was a bit lower than I would like. But there is a lot of summer ahead, so the work will get done. Next week I am planning on heading to the area around Quincy, CA and Bucks Lake to poke around, and hopefully fine more Evening Grosbeaks who will listen to my recordings and let me know what they think of them!

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While camping last week in the Sierra foothills, I got to witness a wonderful event; the first flight of a Common Raven. I have been fortunate enough to have seen many birds leave their nest for the first time and venture out in to the world. It always excites and inspires me. It is a view of the future, what will this new life include? It is a continuation of the past, linking each individual to their ancestors. It is a reminder that on this great web of evolving lineages, we are all connected to one another.

This particular first flight was, admittedly, not wildly successful. The ravens had built their nest in a large spruce tree that was just a dozen or so yards from where we were camped with a group of our friends. On Tuesday, the 17th of June, one of the young ravens decided that the time was right. It spread its wings and leaped out of the nest. It did not get far, as it glided right over our campground and crashed clumsily into a tree. it then attempted to flap its way higher up the tree, but only succeeded in knocking itself lower and lower until finally it fell out of the bottom branches of the tree and onto the ground about 4 feet from where my 1.5 year old daughter was playing with her friends! They all looked at each other for a moment. The kids looked at the raven with surprise and the raven look at the kids with the same expression. After a few seconds just staring at each other, the bird turned and hopped off through the trees. Rather soon, one of the adult ravens had found the wayward youngster and commenced yelling at the young bird until it found a tree with a lot of low branches and was able to scramble awkwardly up off the ground.

Over the next couple of hours, two more young ravens dropped out of the nest ending up scattered around that patch of forest. All seemed healthy and strong and began to explore their, suddenly expanded, world. The adults certainly had their work cut out for them as they tried to feed and keep track of the three young birds wandering through the trees, and the forest was loud with all of them calling back and forth to one another.

A pretty exciting and memorable event for all concerned!

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On our way up into the Sierra foothills for a few days my wife and I got to see something amazing! We were driving along a beautiful curving stretch of forested road when we saw movement off to our right. Up off the side of the road, two Turkey Vultures took flight. There was a deer carcass in the ditch that they had both been feeding on until they were disturbed by our passing car. One of the Turkey Vultures flew away from the road farther into the trees. The other decided to fly across the road, directly in front of our car! This startled us, and apparently did worse to the bird, because this is when the amazing thing happened. The Turkey Vulture threw up!

This is a behavior that many New World Vultures do, and may have several functions. One is called defensive vomiting and is used in predator deterrence. If a vulture feels threatened by a predator it may vomit onto the predator, coating it with smelly, partially digested carrion. I can imagine that being a very unpleasant experience, and wanting to leave as quickly as possible, and apparently many predators agree. A competing hypothesis is that the vultures vomit is a decoy. They give the predator something that it may want to eat, the vulture’s partially digested food, and while the predator is busy with that the vulture gets away. I have not found a lot of support for this hypothesis, but it is out there and has not been well investigated. A third reason that vultures vomit is to become lighter. Vultures are somewhat boom-and-bust feeders in that they cannot count on finding a carcass every day. This means that when they do find one, they eat a lot so that they have energy to see them through until the next carcass find. The down side of eating a lot of meat is that it is heavy which makes a fast take-off rather difficult. If a full vulture is startled, and needs to get off the ground and up into the air and out of reach quickly, one fast way to lighten the load is to empty their stomach! This is exactly what I think the vulture we saw was doing. On suddenly finding itself in front of our oncoming car, and wanting to gain altitude as fast as it could, it threw up the deer meat it had just eaten, and thereby made itself lighter. Actually quite ingenious!

What made me especially excited about this whole thing was that I had never actually seen this behavior before! I had read about it and heard other people talk about, but I had never witnessed it myself! I felt so lucky. It was one of the high points of my day!

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I just read an article, and then the paper it was based on, about songbird migration. It was published by a group from the Cornell Lab of Ornithology (including one person I used to work for). They used eBird records to examine where and when songbirds migrate and how these migratory movements correlate with weather patterns. What they found was that songbirds use different migratory routes in spring vs. fall,  moving in a roughly clockwise pattern. This makes the routes match wind patterns such that the birds take advantage of the strongest tailwinds in spring as they head north to their breeding grounds and face the weakest headwinds in fall as they move south to their non-breeding grounds.

I really like this study for several reasons. One is that much of our understanding of migratory movements in birds is based on waterfowl banding results. This is because there is a huge waterfowl data set due to hunters who report the bands on birds they shoot. This results in something like a 10% recovery rate for banded waterfowl (in comparison, songbirds banding has something like a 1%, or less, recovery rate for bands). However, any information that is gained by studying waterfowl movements may or may not be applicable to other birds. For example, most waterfowl are fairly strictly limited in the type of habitat they can use. Other birds are much more general, so the patterns may well be different. As our abilities to track bird movement have increased, our understanding of migration has also increased, and (as in so much of life) the picture is more complicated the more we learn. So this new analysis broadens our understanding of what migrating birds do. Waterfowl generally use one of four fairly narrow migratory corridors, called flyways, as they move north and south each year (the four flyways are the Pacific, Central, Mississippi, and Eastern). Songbirds, it turns out, use much wider swaths of the landscape which can be roughly divided into three flyways (Western, Central, and Eastern), and the areas used within each swath are different in spring (more to the west) than in fall (more to the east).

Another reason that I like this study so much is that is relies on citizen scientist. The records that the authors used were from eBird, which is an online database run by Cornell that anyone can add to. It is a way for birders to post their sightings and then see how those sightings fit into the larger picture of what birds are doing across the state, country, continent, or even hemisphere. By tapping into this vast knowledge base, the authors were able to examine where birds were being seen and when at a broader geographic scale, finer resolution, and including more species then ever would have been possible if the authors had tried to collect the data themselves. So, this study stands as yet another example of how important individual birders are to bird research and conservation. It is also another reminder of how much value there is in birders and ornithologists talking to each other!

So, a great study with interesting results and creatively using a citizen science data set. What could be better?

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