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Posts Tagged ‘Yolo Bypass’

If you are in the Davis or West Sacramento area in the late summer or early fall, and have an evening to spare, go and find a spot where you can sit beside the Yolo Bypass Causeway. This is where highway I-80 crosses over the Yolo Bypass.

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Streams of Mexican Free-tailed Bats over the Yolo Bypass

Just as the sun begins to set, you will see an amazing sight. Columns of bat will flood out from under the bypass and stream across the sky in sinuous ribbons. About a quarter of a million Mexican Free-tailed Bats (Tadarida brasiliensis) live under the bypass this time of year, and every night they pour out and spread across the surrounding area to find small flying insects to eat.

These bats are incredible! They can fly about about 100 miles per hour, making them among the fastest mammals in the world! Remember that Cheetahs are the fastest land-mammal, but bats have them beat by a healthy margin. These bats can fly as high as a mile above the ground, and can forage out distances of several miles from their night roost before returning around dawn to sleep. Using their sonar they can detect and pinpoint the exact position of little insects flying through the air and then capture those insects on the wing, at speed!

My wife, daughter, and I joined some friends and went out for an evening visit to see the bats about a month ago. I was a spectacular evening in the Yolo Bypass Wildlife Area. We saw lots of Swainson’s Hawks; herons, egrets, and ibis galore; some of the biggest Western Saddlebags (which is a species of dragonfly) I have ever seen; and then we got to the causeway.

When we arrived, the sun was still a touch above the horizon, so we had some time to stand around the dirt road that runs parallel to I-80 and chat and watch the sunset. We got a very nice surprise when an adult Peregrine Falcon flew past and landed in the top of a tree a little ways to the west of us. I was so excited to see this bird that, in turning around for a better look, I clumsily stepped on my wife toes (sorry sweetheart)!

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Mexican Free-tailed Bats as they leave from under the Yolo Causeway.

As the light began to fade, we started seeing little movements under the causeway. The first bats were starting to move. Interestingly, the bats do not wake up, take flight, and simply fly out from under the causeway wherever they happen to be. Instead, they wake up, take flight, and then fly directly under the causeway for a few hundred yards before turning a sharp left, and lifting up into the open sky. I have no idea why they decide to do this, but volunteers at the Wildlife Area know it is gong to happen so consistently, that they can tell you exactly which tree the bats will fly out near.

The numbers of bats moving under the causeway built and built until there were bats streaming along between the support pillars. Then they made that left, and out in to open they came! A snaking stream of bats began raising and twisting into the sky! Thousands and thousands of bats following one another out from where they had been sleeping to look for food. As we watched the seemingly endless flow of bats, we got a very cool surprise. That Peregrine Falcon that we had seen earlier came back. It started strafing through the flow of bats. It was hunting bats!

I have seen this behavior of raptors hunting bats as they leave their night roost on video before, and it is pretty spectacular to see on a screen. Seeing it in real life was thrilling! After a couple of passes, the Peregrine made a quick move to one side, and suddenly it had a bat in one talon! It flew off and out of sight carrying it’s dinnertime snack.

The rest of the bats were generally nonplussed by the Peregrine attack, and keep streaming and streaming into the coming night.

Finally, the last bat that was going to leave had departed, and the darkness was getting deep enough that we would not have been able to see the bats fl by even if they were there, so we piled back into our cars and headed for home.

All in all, a terrific way to spend and evening!

 

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A couple of weeks ago, I went out to the Yolo Bypass Wildlife Area to see if I could spot the Marsh Sandpiper that had been hanging around for about a week before. Marsh Sandpipers breed in central Asia and migrate south to India and Africa, so finding one in central California is a rarity, indeed.

It was a lovely morning in the marshes of the bypass. I arrived at Parking Lot C around 5:45, well before it got light. I could hear Barn Owls over the open fields and American Bitterns in the tules and cattails. As dawn slowly began to spread her rose-red fingers across the sky, I began to be able to make out shapes in the marshland around me. At first, they were indistinct sandpiper and duck shapes, but as the light grew, they slowly morphed into Greater Yellowlegs and Gadwalls. These were soon joined by American Avocets and Cinnamon Teal, Black-necked Stilts and Mallards, Killdeer and American Coots. These birds were joined by a half dozen Long-billed Dowitchers, a Semipalmated Plover, and a lovely mixed flock of Least Sandpipers and Dunlin, the later sporting their breeding plumage replete with black belly patches. As I stood and watched the shallow water less than 20 feet in front of me fill with birds, I noticed a sandpiper that looked distinctly different from the rest. It was closest in shape and size to the Greater Yellowlegs but it was somewhat smaller, much lighter in color, and had a delicately refined and slender black bill.

Marsh Sandpiper by Douglas HerrIt was the Marsh Sandpiper!

A large, white pickup truck pulled into the parking lot. A figure stepped out and as he walked towards me, donning binoculars, the man asked, “Is it here?” There was no need to specify what “it” was. I happily told him yes, and that it was actually right in front of us. He told me that he had just driven all the way from San Bernardino in southern California to see the bird and was then going to be driving back down to be back home that evening!

I stayed for another 20 min or so, watching the Marsh Sandpiper forage and come and go along with the other birds. Having that many species of sandpiper right in front of me would have been a wonderfully special morning even without the Marsh Sandpiper. It is amazing to see biodiversity so obviously demonstrated. That many species coexisting translates into that many niches and that many food supplies, and the ripple effects continue.

On my way driving out of the bypass I passed a stream of vehicles on their way in. Many drivers gave me questioning thumbs up which I enthusiastically returned. Many others were focused on getting to their destination, and the bird they hoped they would find there. Hunkering low over their steering wheels, their eyes fixed on the road, I knew they were in for a treat.

It was fun watching all those birders coming in to see the Marsh, but I knew that I had gotten something special. I had been lucky enough to encounter the bird myself instead of having it handed to me by someone else. I had also been lucky enough to see the bird all alone for a while, not standing amongst a group.

This was one of those birding experiences that stay with me for a long time. I was walking on air all that day, and for several days after. It was one of those experiences in birding that explain why people will drive 400 miles each way to see a bird, and even now, recalling that morning in the marsh with the Marsh makes me smile.

Marsh Sandpipier by Gary Nunn

Marsh Sandpiper (Photo by Gary Nunn).

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