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Archive for the ‘Wading Birds’ Category

A few years ago I wrote a post on niche partitioning amount herons and egrets. That post was inspired by watching several species of herons and egrets foraging for food along Putah Creek near Davis, CA, and the resource they were partitioning into niches was food.

Recently, as part of my work at the Sacramento-San Joaquin Delta Conservancy, I encountered another example of niche partitioning by herons and egrets. This time, the resource these birds are partitioning into niches is nesting trees.

One of the grants that I manage at the Delta Conservancy is at the Cosumnes River Preserve and it includes and grove of large Valley Oak Trees that many herons, egrets, and cormorants use as a rookery (a rookery is a colony of breeding animals, generally birds). One way that the various species have evolved to utilize the same trees, and yet avoid directly competing with each other, is for each species to utilize a different part of each tree to nest in.

Great Blue Herons typically nest on the very tops of the crowns of trees, Great Egrets typically nest only in the upper one-third of the canopy, Snowy Egrets typically nest in the middle one-third of the canopy, and Black-crowned Night-Herons prefer to nest in the lower one-third of the canopy (see the image below).

Niche partitioning of nesting locations within a tree by heron and egret species

I think this stratifying of nesting locations is amazing! Species have evolved to fill so many different niches, and so many niches can be divided into finer and finer gradations. I wonder if there is really any limit to how many species can evolve, and how complex an ecosystem can develop, in a give location.

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Information is important. With information each of us as individuals, and our society as a whole, can learn about the world. With information, we can all make decisions that make sense. With information, we can all discuss ideas.

Without information none of that is possible. Without information, we are, at best, at the mercy of our current, limited knowledge, and our base instincts. Without information we are, at worst, at the mercy of the limited knowledge and instincts of someone else.

This is why the gag order, and insistence that all reports and data be pre-screened before release to the public, issued by the President to the EPA are so concerning to me, and I think should be so concerning everyone else. This is exactly the kind of action that limits access to, and spread of, information. It will only hamper all of our abilities to operate as rational, critically thinking individuals. It is the kind of action that is put in place to control what we, as citizens, know and when we know it. This is censorship and it has no place in science or a free society.

#thisisnotnormal

pansy-white-blue

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It has been 14 years since the first printing of the first edition of David Allen Sibley’s Sibley Guide to Birds. It was a wonderful book and stood out, at least in my mind, as the best guide to come out since Roger Tory Peterson’s guides to eastern and western birds. Now Sibley has produced his second edition, my copy just arrived in the mail yesterday. And this new edition has a lot of changes from he old one.

The first thing that struck me were the colors. This new edition has generally bolder, darker, richer colors than the first edition. This change may serve to highlight plumage characteristics and draw attention to color contrasts, and so may make the guide more user friendly. However, there is always a danger when attempting to improve on reality and the result will be distorting reality. Overall, I really like the richer colors, but I do think that on some of the birds, such as the California Towhee, it may have gone a bit too far.

A second major change is that the families of birds now appear in a very different order. Traditionally, bird guides have been formatted so that they present the groups of birds in an order that follows the evolutionary history of birds. In most guides this has meant that the first groups are the Loons then the Grebes then the Albatross and Petrels. However, with ever more detailed and accurate DNA sequencing abilities, the evolutionary history of birds has been going through several rounds of shake-ups, and Sibley’s second edition reflects the more current understanding of how birds have evolved. Now, the first groups shown are the Ducks and Geese followed by the Gallinacious birds and then the Loons, and the altered order of bird families continues throughout the rest of the book. I really like that the order of bird families has been changed. It means that we all have a better understanding of evolution. I am sure that some people will be annoyed at the new ordering, and may feel a bit disoriented when having to re-learn where to find a particular group of birds, but our knowledge is always changing, and the resources we use should reflect those changes.

A third big change is the addition of 111 rare species. These are species that are generally found on other continents, and that have been recorded a very small number of times in North America. At first, I thought that this would simply clutter up the guide with a bunch of birds that basically no one sees, and that they would distract from the birds that people are generally looking for when they open their bird books. But, on further reflection, I have actually really like having all these new birds. It gives us all a better understanding of, and exposure to, what birds are out there. I think that if we as birders, all have a more global understanding of our favorite taxa, that can lead to nothing but good.

One very minor bone to pick is something that was pointed out to me by the late, great Rich Stallcup. He noticed that the Wrentit had a somewhat worried expression and that this was not really representative of the fierce Wrentit spirit. In the new edition, the Wrentit still looks worried.

So, overall, I really like the new Sibley Guide to Birds a great deal and am looking forward to my next opportunity to use it. If I find a White-crested Elaenia I will now be able to identify it!

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My first memory of Rich Stallcup is actually not a bird memory at all, but rather a frog memory.  I was probably about ten years old when my mother, brother and I joined him on a bird walk.  But the very first thing he stopped to show the group were several Bullfrogs.  He got his scope on them and let us watch them breath.  He told us about how they were an invasive species and voracious predators that were eating the tadpoles and larva of other animals and so driving down their populations.  My second memory of Rich is a bird memory.  We went on a bird walk to Limantour Beach that Rich was leading that focused on gull identification.  I remember standing looking at a large flock of gulls and listening to him point out the subtle differences between different species, and the even more subtle differences between different aged birds of the same species.  I remember being amazed at the level of detail that he could notice and even more amazed by the concept that there was so much more detail out there to be noticed then I had ever realized before.

These memories, and so many more, point out what I feel were some of Rich’s greatest qualities.  He was a naturalist in the truest sense of the word.  He was the best birder I have ever known with an encyclopedic knowledge of birds, but he also knew tremendous amounts about mammals, reptiles, butterflies, and dragonflies.  He even kept a wildflower life list.  In an age of ever increasing specialization on smaller and smaller scales of knowledge, Rich went the other way and proved that a person does not have to choose between being a jack of all trades or a master of just one, but instead could master quite a few.  It is a lesson that I have tried to learn and an ideal that I continue to strive for.  And his attention to detail was incredible.  While standing watching a group of Bushtits work their way through a willow stand, he finally decided that he was not missing any other birds in the flock when he started recognizing individual Bushtits in the flock!

Of course, Rich’s professional accolades are many.  One of the prominent discoverers of the amazing natural history of Point Reyes and the fact that the outer point acts as a tremendous vagrant trap attracting unusual birds from across the continent when they are disoriented by a predator attack or a storm.  The outer point now also attracts birders from around the world.  Rich was also one of the founders of the Point Reyes Bird Observatory, an organization that is now one of the foremost international conservation NGOs.  He has written books, papers, and articles; and also led countless bird walks and pelagic birding trips, all with the aim of introducing people to nature.

I had the good fortune to be able to bird with Rich for many years.  When he and Ellen Blustein started the PRBO Youth Bird-a-thon Team in 1999, the four founding youth members were myself, my brother,and two of my best friends.  I have continued to participate in that event ever since.  Even after I got old enough that I could not count as a youth anymore, Rich seemed happy to have me stay on as a mentor to the incoming generations of youths.  When he learned that I was expecting my first child he told me that, as long as the kid was more than two days old, I should bring him or her on the Point Reyes Christmas Bird Count!  I was very happy that he was able to meet my wife a couple of times, and saddened that my child will never get the chance.

Rich Stallcup died on the 15th of December, 2012 of Leukemia.  His loved ones were at this side.  He was a naturalist who inspired me and many others with his knowledge, passion and generosity, and he will be greatly missed.

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My  wife and I moved into our new place in West Sacramento a couple of weeks ago, and I have started exploring the nearby area to discover its birding potential.  Even though there is a fair bit of industrial development, and a lot of residential development, the birding is actually quite good.  This area has an extensive network of canals that help to manage water flow around the Port of Sacramento and in the Sacramento River.  These canals are all lined with Cattails and Tules which provide habitat for a number of species.  Associated with these canals are a number of bodies of open water.  These range in size from only about a quarter of and acre to large lakes like Lake Washington.  Many of these bodies of water are lined with willows, oaks, and cottonwood trees which create edges of riparian habitat.  Together the open water and riparian corridors attract even more species.  The list of species I have seen so far is at the bottom of this post.  I have not seen anything particularly unusual, but fall migration is still building up, so there are lots more birds on their way through.

Walking these canals and water edges has really impressed upon me how important even small areas of habitat can be.  These waterways provide stopover sites for lots of birds and they are pretty much in peoples back yards.  They take up pretty small amounts of space, yet yield a  very large benefit to wildlife.  I will certainly be spending a fair bit of time exploring these urban waterways and seeing what turns up.

Birds: Red-winged Blackbird, Marsh Wren, Common Yellowthroat, Wilson’s Warbler, Yellow Warbler, Long-billed Dowitcher, Black-necked Stilt, Canada Goose, Lesser Scaup, Mallard, Killdeer, Great Horned Owl, Red-tailed Hawk, Red-shouldered Hawk, American Kestrel, Western Scrub Jay, Anna’s Hummingbird, Bewick’s Wren, Lesser Goldfinch, House Finch, White-crowned Sparrow, Mourning Dove, American Coot, California Towhee, Spotted Towhee, Song Sparrow, American Crow, European Starling, Rock Pigeon, Black Phoebe, Chestnut-backed Chickadee, Oak Titmouse, Green Heron, Great Egret, Snowy Egret, Great Blue Heron.

Mammals: Sacramento Cottontail, Raccoon, River Otter, Eastern Fox Squirrel.

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I went birding at the Yolo Bypass Wildlife Refuge, yesterday morning.  It was lovely to watch the refuge wake up in the morning to a beautiful sunrise over the Sierra.  Got lost of close and excellent looks a bunch of Ciconiiforms: Green Heron, Great Blue Heron, Great Egret, Snowy Egret, White-faced Ibis, Black-crowned Night-Heron, American Bittern.  Also watched a Barn Owl hunting over the marsh just went I arrived.  It was soon replaced by Northern Harriers and White-tailed Kites quartering above the cattails and tules and rice paddies.  It has often been observed that no two species can occupy the same ecological niche in the same place at the same time.  The Harrier, Kite and Owl all are hunting for the same basic prey, but they are active at different times.  This is an example of temporal partitioning.  The water level at the refuge is still being kept pretty low, but in areas that did have standing water I found Mallards, Gadwalls, Black-necked Stilts, Marsh Wrens, Pied-billed Grebe, and Double-crested Cormorant.  Lots of Black Phoebes and Savannah Sparrows, and a few Red-tailed Hawks, were also present.  An early migrant that was exciting to find was a group of about a dozen Northern Pintail!  Northern Pintail are one of the earliest migrating species of waterfowl, so this is just the start of the massive migration of ducks and geese that will be arriving in central California in the next few months.  Two species that I found that I do not get to see often were a couple of small groups of Horned Larks foraging on the roads and three Yellow-headed Blackbirds (two males, one female) mixed in a group of Red-winged Blackbirds.  Both beautiful species.  All in all, it was a really wonderful, relaxing and refreshing morning.

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I was out walking at the Yolo Bypass National Wildlife Refuge, yesterday, and was treated to the sight of a flock of about 30 White-faced Ibis flying overhead. This is one of the species that I always look forward to seeing in the summer, here in Central California. They are beautiful and elegant birds, and seeing them always seems somewhat exotic feel, like you are in the tropics somewhere. The breeding range of this ibis is highly variable from year to year depending on water levels and food availability. Large numbers may nest in a general area one year, and none may be there the next. The total range that they can potentially breed in encompasses a huge area of the western U.S. This makes monitoring of their population levels rather hard because any survey would have to regularly cover the entire potential breeding area to accurately count the actual number of birds in any given year. No small task! Due to the fact that the White-faced Ibis often feeds in agricultural lands, they may be exposed to many of the pesticides and fertilizers that are used in growing our food. This heightened exposure potential makes them a possible “canary in the coal mine,” and so a particularly important species to monitor. This species’ winter range mostly resides in Mexico, and little or nothing is known about this part of their annual cycle, a fact that is true of so many bird species. A wonderful bird that I hope you all can get out and enjoy before they head south in a few weeks!

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I have been seeing lots of Cattle Egrets around Davis the past couple of weeks.  Before a couple of weeks ago, I did not see any moving through the skies over Davis, but now I am seeing them frequently.  They have been in groups that range in size from five or six up to flocks of 25!  Very beautiful birds.  From what I know of their annual schedule, some should be starting to molt (if they started breeding early in the season and have already fledged their young) or still have young birds to feed (if they started breeding later in the season).  So, I am guessing that the groups I am seeing are family groups of adult and juvenile birds or perhaps a few family groups that have merged together.  Cattle Egrets are very successful dispersers.  Originally native to Africa and southern Europe, they are now found on every continent except Antarctica and also on many remote islands, and they have done so without human intervention crossing from Southeast Asia to Australia in the 1930s and crossing the Atlantic Ocean from the west African coast and making landfall in northeastern South America in the late 1800s.  The first recorded breeding pair was in Florida in 1953.  In South Africa, where their population is generally sedentary, individuals or small groups of juvenile birds have been frequently observed to go long distances when leaving their natal area in search of new breeding areas.  This behavior is common to many of the Egrets and Herons, but it is especially well developed in the Cattle Egret and it seems to be one of the major factors that have allowed them to cover the globe.  In fact, the dispersal of individuals across large bodies of water is probably still occurring because these birds are regularly seen be passing ships far out at sea.  With so many examples of species being introduced by humans into new areas, I think it is really cool and interesting to see an example of dispersal happening naturally, as it has been happening for millions of years.

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I went for a walk along Putah Creek yesterday at the South Fork Preserve.  The early morning was windy and not yet hot, but the sky was clear and the sun was bright.  When I got to the first creek access point, I was treated to a view downstream of the creek scattered with egrets and herons (all members of the family Ciconiiformes).  Usually there are one or two, but I have never seen this many along the creek before.  About half-a-dozen Black-crowned Night Herons were perched in some dead and fallen branches just above the water line.  Three Snowy Egrets were just beyond them foraging in the shallows skittering their feet around in the mud and silt and darting off after food when it was disturbed by the egret’s agitated foot movements.  A bit farther into the channel, stood 5 Great Egrets.  They were all hunting through an area of the creek that was thick with aquatic plants and alga.  They stood almost motionless, waiting for some unsuspecting prey to swim by.  Out in the deeper water in the center of the channel were the 3 Great Blue Herons using the same hunting strategy as the Great Egrets, they stood waiting.

Watching these birds all crowded into the same area got me thinking on how each species utilizes a different part of the habitat and has characteristic behavioral differences that help then to do so, a concept known as niche partitioning.  But which came first, the different species or the different behaviors?  Perhaps populations of ancestral Ciconiiforms became somehow reproductively isolated and so became different species, and then these different species developed different behaviors.  Alternatively, perhaps different behaviors arose in that ancestral species that allowed some members to use one part of the habitat better, and other members use a different part of the habitat better, and this then led to assortative mating and speciation.  And the answer is not necessarily the same for all species, in fact it is almost certainly not.  But how often does reproductive isolation come first?  How often is behavioral differentiation the inciting incident?  No one is really sure, but I find it fascinating to think about.  Gaining a greater understanding of how these different processes work and interact will give us a greater understanding of evolution and natural selection as a whole.

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