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Posts Tagged ‘Swainson’s Hawk’

The Sacramento-San Joaquin Delta Conservancy (where I know work) was allotted $50,000,000 from the voter approved Proposition 1 for projects that will enhance habitat, improve water quality, and/or increase sustainable agriculture in the Delta. These funds are to be given out over the course of five years, starting with the first solicitation in fall of 2015. The Delta Conservancy created a competitive grant program where applicants can send in proposals and Delta Conservancy staff, with the input from other experts, determine which proposals have the best chance of success and will enact the most valuable projects. This first round of projects could be planing projects of up to $100,000 or implementation projects of up to $2,000,000. A major component of my work has been to help administer this grant process and evaluate the proposals that have applied for the Delta Conservancy’s Prop 1 money in this first year. We, the staff, shepherded projects through the process and made recommendations to our governing board, who voted to approve or reject the various projects that were submitted. Going forward, I will continue to be highly involved in the next 4 years of funding cycles.

Swainson's Hawk - Jabari Bellamy

Adult Swainson’s Hawk hunting over a California grassland (Photo compliments of Jabari Bellamy)

One of the projects that applied for the Delta Conservancy money was submitted by the Environmental Defense Fund to convert approximately 300 acres of private agricultural working land currently used for growing various row crops into pastureland bordered by hedgerows of native vegetation. This crop conversion will encourage Swainson’s Hawk prey species and so make this land high quality foraging habitat for Swainson’s Hawks. This project scored in our competitive process and was approved by our board (pending a some final administrative paperwork). To read more about the project, and find out more about the work that the Environmental Defense Fund is doing, check out this link to their write up of the project.

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As my wife and I were driving from our apartment to downtown Davis, today, we watched two adult, light-morph Swainson’s Hawks diving and chasing each other over I-80.  They were not acting especially aggressively towards each other, but rather were flying after one another in a more playful manner.  At one point, in the midst of their swooping and diving, they both gained a fair bit of altitude, flew straight toward each other, and locked talons!  They began to fall and spin directly toward the streaming highway traffic below.  For a brief moment, I thought I was about to witness a tragic crash, but then separated well before they actually got down to car and truck level.

I have only rarely seen this talon grappling behavior before, and never done by a pair of Swainson’s Hawks.  It was very dramatic!  This is usually done by birds of prey during the courtship period when two birds are setting up a territory and settling on each other to have babies with this year.  Late June is not when this kind of thing would be expected seeing as most all the birds are now in the hatching eggs stage of the breeding season.  However, just like humans, raptor pairs occasionally take a few moments out of their busy days to spend some quality time with each other.  This time serves to reenforce and strengthen their pair-bond, and may contribute to higher rates of nest success.

So, take a few moments, find your sweetheart, and reenforce your pair bond…and by that I mean that you should lock talons together and spin a little!

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Birds around Davis are in high nesting gear, right now, and along with nest building comes conflicts over territories and mates.  These conflicts can be sneaking stealth raids, small border skirmishes, or fully pitched battles with the combatants hitting hard and fast.  I have witnessed several such battles just in the last few days.  The first was a contest between two male House Sparrows.  They were locked, bill to bill, on the ground rolling over each other as each pummeled the other with its wings.  This wrestling match went on for several minutes and the fact that I approached to within 10 feet or so did not seem to merit any form of acknowledgement.  Finally, one broke away from the others grasp and fled up into the low branches of a nearby tree.  It was immediately pursued by the other who drove the fleeing looser out of the area  entirely.  The winner then flew to a female who had been sitting in tree watching the whole conflict and deciding which male was the worthy mate.

A second vigorous battle I watched was between two male Anna’s Hummingbirds.  This struggle was all aerial!  No fighter pilots in the world have the ability to match what these two birds could do!  Like the House Sparrows, these hummingbirds were locked in a wrestling match, but theirs’ was a wrestling match in three dimensions as they tumbled over and over each other through the air.  Then they would break apart, and one would tail chase the other until they met again and battle was rejoined.  The speed of the whole thing was also quite impressive.  Their combat covered a whole field and in only a matter of 30 seconds or less the conflict was over.  The winner landed in the top of a bush and started bugling his victory at the top of his lungs, and the looser slipped away to try his luck elsewhere.

The last battle of the past week was directly over the quad on the U.C. Davis campus.  It involved four Swainson’s Hawks that were engaged in a bit of a territorial dispute.  Two if the birds, presumably a pair, were very aggressively chasing the other two, also presumably a pair.  The chase twisted and turned through space with the birds diving on each other repeatedly.  One such dive was done with such vigor that it sent the receiver crashing into the top of one of the oak trees that line the quad!  Finally, the resident pair convinced the interlopers to move on.  What really surprised me about this particular battle was that, at least from what I could tell, none of the 50 or 60 people milling about the quad noticed!

So, all in all, a pretty dramatic time here in central California.

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The birds of prey, here in Davis, are in full nest-building mode.  Yesterday I followed an adult, light morph Swainson’s Hawk that was carrying a stick and so found my first Swainson’s Hawk nest of the year being built near the top of a redwood tree on campus.  This is the exact spot where a pair nested last year and is also where I saw my first Swainson’s Hawk this year.  I have no idea if this is the same pair that held this territory last year, but it does seem likely.

Additionally, today I saw a White-tailed Kite in some grasses on the ground.  As I watched, it took off with a bundle of dead grass in its beak.  I was able to follow this bird to my first White-tailed Kite nest of the year.  This nest is in the very top of a Valley Oak out near my lab.  The tree is along a ditch that acts as a riparian corridor, although there is no water on the surface, through the otherwise agricultural land that fills the surrounding area.

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On the 8th of March, 2012, I saw my first Swainson’s Hawk of the year!  I always look forward to when these birds return to central California.  This bird was calling from a perch at the top of a redwood tree on campus.  It is a spot that seems to be favored by Swainson’s Hawks, as last year a pair set up a territory and nested in the same group of trees.  I wonder if this is one of the same birds.  Now, about a week after that first bird arrived, Swainson’s Hawks fill the skies over Davis as the bulk of the returning population begin to arrive.

Swainson’s Hawks undertake one of the longest migratory routes of any raptor in North America.  They leave from the plains of the continental USA and southern Canada in the early northern hemisphere fall and fly to Argentina.  There, they spend the southern hemisphere summer eating mostly insects.  Interestingly, not all the Swainson’s Hawks go on this long migration.  The birds that breed in California, which is a population that is somewhat separate from the rest of the species, have been found to generally only go as far as Baja California, Mexico.  What makes this group stop so much sooner than the birds that breed in the great plains?  Do any birds from the California population go to Argentina?  Do any birds from the great plains stop in Baja?  I don’t think anyone knows the answers to these questions, but they would be awfully cool to find out!

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