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Posts Tagged ‘Habitat Use’

The idea of a wetland that can move from place to place is an odd one, but in many ways it is not a new one. Basically, a walking wetland is when someone floods a piece of land and lets a wetland grow there for a while. Then, after some pre-determined amount of time has passed, that piece of land is drained and a different piece of land is flooded. A wetland is then allowed to grown on the new piece and, viola, the wetland has walked!

This technique is a lot like crop rotation schemes that have been around for just about as long as agriculture. Letting land lay fallow lets that land recharge some of its nutrients and so be more fertile the next time a crop is grown on it. Walking wetlands are just another type of rotations, but this rotation is to cover the land with shallow water. Not much water is needed to make this work. Generally, about 4 inches is the average depth! Letting the land be flooded in those 4 inches for from 1 to 4 years lets amazing things happen!

Walking Wetland 01

First year walking wetland in the Klamath Basin.

For one, a lovely wetland springs up quite quickly. In the first year, the area is generally covered in grasses and other fairly short plants that only raise above the water a relatively short distance and that grow in a fairly open pattern with lots of space for shorebirds to walk around and forage. In the second year, tules and cattails grow up. This form tall and dense stands. The small open patches are preferred by a wide range of duck species though the shorebirds don’t tend to like this habitat as much. In subsequent years, some habitat modification, such as mowing, is generally needed to keep the tules and cattails at a level that still allows for birds and other wildlife species to access the wetland. Otherwise the stands of tules and cattails grow so dense that only a few species will utilize them.

Another amazing thing is that some crop pathogens that live in the soil drown. Many pathogenic microbes cannot survive a year or two of being submerged. Impressively, many beneficial soil microbes actually can survive this long underwater, so when the land is drained, the good microbes are still present and many of the bad ones are gone! This has an economic benefit because growers then need to buy less pesticides. This has an environmental benefit because grower need to apply less pesticides.

A third amazing thing is that all the birds that come and use the wetland leave their waste behind! Bird guano is fantastic fertilizer, and having a few thousand ducks, geese, and shorebirds wandering around can result in the grower needing to buy and apply less fertilizer and also lead to a boost in crop production!

Walking Wetland 02

An older walking wetland in the Klamath Basin.

Along the Pacific Flyway, walking wetlands have been really pioneered in the Klamath National Wildlife Refuge along the California-Oregon boarder, which is home to the first officially titled Walking Wetlands Program. It has since also been adopted in the Skagit Valley in northern Washington state. Additionally, several groups in central California, including the Sacramento-San Joaquin Delta Conservancy where I work, are looking at using walking wetlands in the California Delta.

For better or for worse, setting aside habitat exclusively for wildlife use is not going to be able to secure enough land to protect that majority of species. Instead, finding ways for agriculture and wildlife to both succeed is the only way that longer-term conservation is going to be successful, and walking wetlands are a terrific example of what that can look like.

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You are walking down a trail in a city park right here in the city of Berkeley. As it winds its way between huge boulders and beneath overhanging bushes, your attention is drawn up into a nearby tree by the sound of scratching. There, a squirrel is scrabbling up the trunk of a tree. As it ascends you notice a thick mat of sticks higher in the tree, way up near the tree’s crown. Is it the squirrel’s nest? The squirrel climbs higher, and then moves beneath the lower edge of the stick platform and then up around the side. As the squirrel begins to get on top of the mass of sticks, it is met with the oncoming rush of the beak and talons of a female Cooper’s Hawk. The mass of sticks is not squirrel’s home, it is the Hawk’s. The squirrel is in full retreat now, and the Cooper’s Hawk in full pursuit. The squirrel begins racing in the direction in which it can go the fastest, strait down the tree trunk. The Cooper’s Hawk immediately drops after it, skimming strait down along the bark of the tree. As the hawk gains, the squirrel jumps, letting go of the tree completely and free-falling into the bushes below. It is only then that the hawk gives up the chase and returns to her nest.

What you just witnessed was the defense of one of about a dozen Cooper’s Hawk nests in Berkeley and Albany. Cooper’s Hawks in Berkeley? That’s right. These roughly crow-sized predatory birds get along quite well with humans and the cities humans live in. They eat birds and small mammals which they often capture by ambushing their prey in dense vegetation and then chasing it down in a burst of speed. They are superbly adapted to this style of hunting with short rounded wings which give the speed while not getting hung up on foliage and a long tail which acts and a rudder allowing them to turn and twist through thick undergrowth and not lose their prey.

The ability to live well with humans is unusual for a predator. Most birds of prey are too sensitive to disturbance to live in such close contact with humans or need larger areas of open spaces in which to hunt than are available within such a human-dominated landscape as downtown Berkeley, but Cooper’s Hawks find a way. They are so tolerant in fact, that in Berkeley and Albany, more Cooper’s Hawk nests can be found per square mile than in any other recorded area in North America. They nest in mature trees in almost any kind of habitat from quiet city parks to busy city intersections. And Berkeley in not alone in being an urban area that has nesting Cooper’s Hawks. In California, most urban areas have populations. Outside of the state, populations that have been studied in some detail include urban areas of Arizona, Illinois, and Vancouver, Canada.

Beginning about 15 years ago, a group of dedicated volunteers have been keeping tabs each year on the levels of Cooper’s Hawk activity in Berkeley. The group, the Cooper’s Hawk Intensive Nest Survey (CHINS), has divided the 10.4 square miles of Berkeley into smaller units. Each volunteer takes responsibility for one of these units, and searches it to locate and track the presents of Cooper’s Hawks. Searching begins in late January when the hawks first arrive in the area back from their wintering grounds, and continue all through the breeding season until the adults and a new generation of young Cooper’s Hawks depart to return south in August. In between, many observations are made and recorded such as when the hawks arrive, when nest building begins and ends, how many young hatch and when, how many young fledge and when, what they are eating and how much, and finally when the adults and young disperse.

Some the information that CHINS has found is that while Cooper’s Hawks nest in greater density in Berkeley than elsewhere.Also, they are eating a lower number of species then in more rural areas, and of these fewer species a large portion (~33%) are Rock Pigeon, European Starling, and other species that are not native to California. On this limited diet, the hawks are able to breed just fine with most nests fledging 3-4 young each year.

The CHINS project is a branch of the Golden Gate Raptor Observatory, and both are examples of scientific studies made possible by volunteers from the community working to monitor and record raptor populations. Cooper’s Hawks, and birds of prey as a whole, can function as indicators of ecosystem health and stability. This makes them especially important and useful to study, and the fact that individuals from the community are able and willing act as citizen scientists and devote their time and energies to such an endeavor show both that such work can be done and that there is interest and support that such work be done.

To find out more about the CHINS Contact Allen Fish at (415) 331-0730 and find out how you can help protect your raptorial neighbors.

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Speciation takes place when groups that were part of one species become reproductively isolated from each other.  Once the groups have become reproductively isolated from one another, speciation may result from each population becoming more and more adapted to their local environment (natural selection).  The gradual accumulation of random genetic mutations (a process known as drift) can also contribute to speciation, but at a much slower rate.   In the classic model of speciation, the process was only complete when no gene flow occurred between the divergent groups at all.  However, more recent research has shown that species can maintain their distinctness even when small numbers of hybridizations occur.

One way for two groups to become reproductively isolated from one another is by developing different dietary preferences.  This can happen when groups specialize on different parts of a resource (large versus small seeds, or insects that live on the outer tips of tree branches versus inner foliage near the trunk).  This results in individuals of different groups encountering one another only rarely simply because they are foraging in different habitats or different parts of the same habitat.  Diet-driven habitat isolation is different from the patterns of spatial separation I covered in my last post because it is not an geographical accident or some inherent physiological tolerance that is separating members of the two groups.

Dietary preferences can arise by mutation or in response to competition.  Favorable mutations may allow one group to utilize a whole new type of food which opens new habitats for that group to evolve into.  Such dietary innovations can lead to the evolution of different morphological features that further aid in the use the new resource.  These different morphologies can in turn lead to further reproductive isolation, and this process can become a self-reinforcing cycle.  This cycle is also supported by hybrids frequently having morphologies that are intermediate between the two groups.  These intermediate morphologies will likely be inferior to either of the groups and will result in hybrids leaving fewer, or no, offspring.  Natural selection will then favor adaptations to avoid hybrid matings because these matings will be wasted reproductive effort.  Competition can lead to differing dietary preferences by favoring the individuals in a population that are best suited to utilizing the extremes of a resource.  This can occur when competition for food resources is high.  Then if one group is able to utilize one end of a continuum and another group is able to utilize the other end, these populations may become favored because they avoid much of the competition.  Again, hybrids may do poorly because of intermediate morphologies that have evolved in response to the extreme ends of the food continuum, and also because they may have to deal with stronger competition from the other group.

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Yesterday I, my wife, and our ten-day-old daughter went out to bird the area south of Davis, CA. as part of the Winter Raptor Survey that has been started by the Hawk Migration Association of North America (HMANA).  I am on the HMANA board of directors and have been helping to organize this winter raptor survey.  We are hoping it will grow into a nation-wide monitoring system of the raptors that spend the winter months anywhere in North America.  To run a survey route all that is need is a bit of local raptor knowledge and four days a year.  Each volunteer sets up their own route in an area, and then drives that route one day in November, one day in December, one day in January, and one day in February.  After driving the route (which should be between 30 and 100 miles long), and identifying all the raptors seen, the results are entered into an online database and compiled.  Repeatedly surveying the same route several times each winter gives a better measurement of how many individuals and species are using a particular area, and will result in a more accurate overall population estimate.

The route that I am running was established by a former graduate student in the Avian Sciences Graduate Group at U.C. Davis that he used for his masters research (he established many routes throughout California, so if anyone wants to run an established route, contact me).  This route works its way through an area land that is used for crops, orchards, and cattle and sheep range land.  It is about 40 miles long and took us about 4 hours to run (12 to 4). The day was a bright and sunny one with no clouds and a cold wind out of the northwest.

It was a wonderful day of birding, and my daughter’s first birding outing!  She slept in her car seat the whole time except when we stopped to feed her and change her diaper.   In total, we saw 96 raptors of 10 species.  The species were Turkey Vulture, White-tailed Kite, Northern Harrier, Cooper’s Hawk, Red-tailed Hawk, Ferruginous Hawk (a beautifully marked adult), American Kestrel, Merlin, Peregrine Falcon, and Prairie Falcon.

Other birds we saw included Loggerhead Shrike, Savannah Sparrow, White-crowned Sparrow, Golden-crowned Sparrow, American Pipit, Least Sandpiper, Killdeer, Cattle Egret, Great Egret, Great Blue Heron, American Crow, Common Raven, Mallard, Brewer’s Blackbird, Red-winged Blackbird, Double-crested Cormorant, and European Starling.

I am already looking forward to January’s survey!

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This month marks the end of my first year serving on the board of directors of The Hawk Migration Association of North America (HMANA).  HMANA is an organization that is serving as a central clearing house of raptor migration data across the continent.  Member sites upload the count data they have collected, and HMANA sorts it and makes it open and searchable to anyone who is interested.  HMANA also analyses and presents much of the data it collects in their journal, Raptor Migration Studies.  Other than migration counts, HMANA has also been working on a project called the Raptor Population Index which is attempting to track the population status of all of North America’s raptor species.  Yet another HMANA project, and one that I have been helping with a fair bit, is the Winter Raptor Survey.  What we want to set up is a network of survey routes that are run each year and that will allow us to monitor the wintering population of birds of prey in North America.

Winter marks a poorly studied part of the annual cycle in the lives of birds of prey.  Where raptors spend the winter, how many there are, and what they are doing are all questions that have, at best, only general answers.  The studies that have been done have given some very interesting and important results.  In Argentina in the mid-1990s, there were reports large numbers of  Swainson’s Hawks being found dead at their communal roost sties.  In 1995 and 1996 some 6,000 Swainson’s Hawks were found dead at such roosts.  The cause was determined to acute pesticide toxicity.  Since Swainson’s Hawks feed largely on insects during the winter, they were being poisoned when they eat insects that had been sprayed with highly toxic chemicals, or were being sprayed directly when they were perched on the ground in crop fields being sprayed.  Specifically, an organophosphate called monocrotophos proved to be especially deadly to raptors.  This chemical had already been banned in the USA, and the deaths of the an estimated 20,000 Swainson’s Hawks led to the banning of this chemical in Argentina in 1999.  A different study on the winter ecology of raptors that was conducted here in central California found that male and female American Kestrels use different habitats to hunt.  Females generally use the more productive open grassy territories, while males are generally relegated (probably due to their smaller size) to less productive mixed shrub habitats.  Such habitat partitioning is vital to know if conservation is gong to be effective.  If a declining species displayed a similar habitat partitioning, and only one habitat type were known and conserved, the population would still decline.

So, how is the HMANA Winter Raptor Survey hoping to monitor the winter populations of birds of prey in North American?  The goal is to establish survey routes that are run once a month for the four months (November, December, January, and February).  This span of time covers the ‘winter’ months of most raptor species.  Along the routes, which are between 30 and 100 miles long, the habitat is described according to one of the categories we have established and the position and identification of all raptor species seen along the route are recorded.  This survey data is then uploaded to the WRS website.  This data can then be used to track habitat use, landscape and habitat change, raptor numbers and densities, and the interactions between any and all of the above.  So, to all the raptor-philes out there, we need your help!  Now that the fall migration is over, please lend a hand in monitoring raptors in the winter.  Set up a route!

HMANA is largely volunteer run.  Check out the HMANA webpage at http://www.hmana.org/ for general HMANA information and news, and the HMANA WRS webpage at http://wrs.hmana.org for specific details on how to set up and run routes.  While you are at these websites become a member of HMANA!  It is a great organization that is showing what citizen scientists can do on continent-wide scale.

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One facet of my research on the Evening Grosbeak (Coccothraustes vespertinus) that I am hoping to put together is a much better survey of where the different flight call types occur, what they are doing, and what they are eating.  To give a bit of background, five different variants of Evening Grosbeak flight call have been observed.  These different variants have been labeled Type 1 through Type 5, and while the differences are subtle to the human ear, they are distinct enough that with practice they can be identified in the field.  They are also different enough that the grosbeaks themselves can almost certainly tell them apart as well, and so may play an important role in group membership identification.

The geographic ranges of birds that make these different flight call types has been generally worked out.  Type 1 is found mostly in the Pacific northwest and central Rocky Mountains, Type 2 is mostly found in the Sierra Nevada and southern Cascade Mountains of California and Oregon, Type 3 is mostly found around Great Lakes and in New England and southeast Canada, Type 4 is mostly found in the southern Rocky Mountains of Colorado and New Mexico, and Type 5 is mostly found in the mountains of central Mexico and southern Arizona.  I say mostly a lot in that description because there is a lot that we don’t know.  It is known that there is a fair bit of overlap in where the different flight call types have been observed.  In the Sierra, while most of the birds give Type 2 flight calls there are birds that give Type 1 flight call as well.  In Wyoming, where Type 1 would be expected, Type 1 birds are the most commonly observed, but Type 4 birds occur there in smaller numbers as well.  There are also parts of the continent where it is not well understood what type might be the most common.  The area in central Canada that is between Type 1 and Type 3 is filled with question marks.  Nevada and Utah are between the Type 1, Type 2 and Type 4 regions.  This area does not have a lot of Evening Grosbeak habitat, but it seems likely that these birds do occur on high mountain ridges.  They may or may not breed there, but even knowing what birds pass through the area would be interesting.  Another huge area of unknowns surrounds Type 5.  Very little research has been done on where these birds occur, exactly.  Even the portion of the range that is in the USA in Arizona and possibly New Mexico is not well established.

An even less understood aspect of Evening Grosbeak life is that of diet.  Most bird books give the very general “eats seeds and insects” with little or no explanation of what seeds and what insects.  Do birds that make different flight call types eat different foods in their respective different ranges?  No one knows.  When individuals that produce different flight call types find themselves in the same place, do they then retain any differences in diet, or do they all simply eat whatever is around?  Again, no one knows.

So here is my call for aid.  I want to collect information on the calls and diet of Evening Grosbeaks across North America.  This will take a very long time if I do it all myself, but I am hoping that you might be willing to help.  If you are willing to help there are two ways you can.  One is if you see Evening Grosbeaks any where, take a moment to observe what they are eating.  What I am looking for is information on what these birds are eating in the wild, so bird seed out of a feeder may not give the most interesting information, although you never know.  The second way to contribute is if you hear an Evening Grosbeak vocalizing.  If you do, and have any recording device (this does not have to be fancy, I have gotten useful recordings off the recorders in digital cameras), then make a recording.  These recordings will be best if they have the vocalizations of only one bird calling for as long as possible, but any recording will be useful and this includes birds at feeders.  After you have made an observation or recording make a note of the date, time of day, location (be as exact as possible.  GPS locations would be great), and any notes on behavior or habitat that seems interesting to you.  Then send them along to me at anhaiman@ucdavis.edu

This is going to be a long and slow accumulation of knowledge which is why I am starting now.  I will be collecting this information for years.  As you find birds and can pass the information along to me, don’t worry about being too late.  Thanks in advance!

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This past weekend, my wife and I joined the rest of the graduate group that I am in for our annual retreat.  The retreat was a camping trip to Boca Spring campground.  It is a great campground in the eastern Sierra Nevada between Truckee and the Nevada State boarder at about 5900 ft in elevation, and set amongst Ponderosa Pines and the occasional Lodgepole Pine.  Each morning I got up early and went out to do some birding!  On Saturday morning, I walked along forest service roads through the pines and around the edges of wet mountain meadows amidst the sagebrush.  It was simply lovely.  And there was some great birding to be had!  At one point, I heard a Northern Pygmy Owl tooting away not far from me, though I was never able to actually see it.  On a small ridge line, I found a mixed flick that included Mountain Chickadee, Yellow-rumped Warbler, White-breasted Nuthatch, Red-breasted Nuthatch, and Pygmy Nuthatch.  From what I can remember, this is only the second or third time I have had a three nuthatch species day!  I was quite thrilled!  This flock was moving through the forest along the ridge.  What really struck me was how unevenly the birds were scattered across the forest.  I had found this fair sized flock of birds all in one place, but before and after, walked through forest that looked the same to me and had the same topography, but had no such flocks.  What made that particular small ridge-line so much better than the one to the east or west of it?  On my way back to camp, I got an additional thrill when I heard, and then saw, Evening Grosbeaks in the area!  Back in the campground, there were White-headed Woodpeckers and a small flock of Western Bluebirds.  Also back in camp, a group of Evening Grosbeaks flew right into the trees above us.  There were about eight birds and all the flight calls that I heard were Type 2, which is the dominant Sierra type.
In the afternoon, we visited the Sagehen Creek Reserve.  This is one of the nature reserves run by the University of California.  We were joined by my advisor who gave us a introductory presentation on the birds and habitat of the high Sierra, and then we all went for a walk to see what we could see.  I added Red Crossbill, Pine Siskin, Hairy Woodpecker, and MacGillivray’s Warbler.  We also found an adult Caddisfly.  Not sure of what species, but I am sure that is this first adult caddisfly I have ever seen!  We also found a Comma which is a species of butterfly.

This was a great trip with great birds and other wildlife, and I even got some scouting done for my own research!  I will definitely be returning to the Boca Spring Campground in the future to find my Evening Grosbeaks.

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