3500 Mile Adventure – North Sterling Reservoir, CO

May 17 and 18, 2021 – Our morning started with dense fog, a relatively rare occurrence in the arid Denver area. The cloud cover promised a day of soft light… and maybe sprinkles. My sister and I headed for North Sterling Reservoir and State Park.

I was intrigued by the description from Colorado Birding Trails of a string of “prairie oases”, lakes and ponds along the winding South Platte River, stretching north and east across the state from Denver. These provide a welcome resting spot after hundreds of miles of dry land along the Central Flyway bird migration pathway, up through the desert panhandle of Texas and the arid plains of eastern Colorado.

Screenshot from Colorado Birding Trails, showing stops on the “Prairie Oases” trail. North Lake Sterling is number 13 on this map.

The satellite image of the area surrounding Sterling, Colorado and North Sterling Reservoir is an elaborate crazy quilt of non-irrigated traditional pastures and hay fields, fields strip-farmed to preserve moisture and top-soil, the smaller circular farms created by older center-pivot irrigation systems, and the much larger circles and pie shapes now possible with newer stronger center-pivot systems. This geometric pattern is laid on top of the ancient riverbed loops and whorls, and the present-day Platte, plaited tan and green.

Screenshot of Google Maps Satellite View, Sterling Reservoir and North Platte River

Canada goslings snuggle up to mama’s flank
1/2500 sec. f/6.3 ISO 1250
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR
(Click on any photo once to enlarge in a new window, and a second time to zoom in; dismiss that window to return here.)

North Sterling Lake has both flat open shoreline, and cottonwood and willow groves. Two pair of Canada Geese shepherded goslings through the open shallows at the edge of the lake. This alert mom guarded her fluffy charges from all comers, including the other goose family, if they got too close or the goslings threatened to get mingled.

Swainson’s Thrush (probably) on cottonwood branch
1/1600 sec. f/5.6 ISO 1250
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

We pursued an elusive brown speckled Northern House Wren (I think) through the tangle of cottonwoods and willows, and she led us to this Swainson’s Thrush (olive backed). This is a new bird for me. I had to study the comparative photos on All About Birds carefully to distinguish between the Hermit Thrush, Bicknell’s Thrush and the Swainson’s, but the buffy eye ring convinced me (then again, I could be wrong – do let me know!).

Male Kingbird among cottonwood blooms
1/2500 sec. f/7.1 ISO 1250
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

The groves of mature cottonwood trees grow happily with their feet in the sandy lake bed covered by shallow fresh water. A Western Kingbird perched momentarily, waiting for the plentiful bugs to fly by, creating this nice silkscreen image.

Kingbird takes flight near Oriole nest
1/4000 sec. f/7.1 ISO 1250
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

The nest near him is not his; I believe it is the nest of an Oriole. The Audubon website has a great article on Oriole nest-building. Both Baltimore and Bullock’s Orioles weave these hanging gourd-shaped nests.

Male Bullock’s Oriole with signature orange eye stripe
1/2500 sec. f/7.1 ISO 1250
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

The trees were full of Bullock’s Orioles, each in constant movement. This one paused for a moment on a willow branch above our heads. I had at first assumed that this was a Baltimore Oriole, but the orange eye stripe is a dead giveaway for the Bullock’s. The Bullock’s were first described and named by William Swainson, in 1827.

Bright yellow male American Goldfinch looking at us over his shoulder
1/5000 sec. f/5.6 ISO 1250
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

American Goldfinches were everywhere as well, and we were thrilled to get this one while he was still for a moment, without branches intervening.

Hiding in plain sight
1/5000 sec. f/5.6 ISO 1250
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

Then, he decided camouflage was a wiser choice. We couldn’t figure out whether he was eating seeds from old dandelion heads, or harvesting the fuzz for a nest, but he definitely had a mouthful.

You can’t see me!
1/2500 sec. f/7.1 ISO 1250
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

A House Finch decided to get in on the fun, but didn’t quite understand the “protective coloration” strategy.

Male House Sparrow in breeding plumage, inside a shrub
1/5000 sec. f/5.6 ISO 1250
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

And back by the parking lot, a wily adult male House Sparrow in breeding plumage carried a mouthful of grass seed deep into the shrubbery and out of sight. My only excuse for this shot is… this is the best representation of how the bird looks and lives, surrounded by protective sticks (my story, and I’m sticking to it!). I’m also a bit tickled that I was able to pierce that tangle of sticks and twigs with my autofocus to see the bird clearly.

“Parking lot” is normally my signal for shutting down the day… but we were not done! My sister upped the game with some suggestions for finding birds along the narrow gravel roads along the South Platte River valley, and we got lucky.

Adult Swainson’s Hawk takes off from telephone pole perch
1/2500 sec. f/6.3 ISO 1600
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

A Swainson’s Hawk (three species in this post identified by William Swainson, how cool) perched on a power pole, and allowed me to creep up on it along the gravel road in time to capture its lift-off. The Swainson’s Hawk migrates each year from Argentina to Alaska and back, breeding in North America and wintering in the temperate climates down south.

Female Wild Turkey, checking her six
1/2500 sec. f/7.1 ISO 1600
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

We had seen Wild Turkeys in the distance earlier in the day, and I had even pursued a hen down an irrigation levee (not a good strategy – just walking, she was able to out-pace me as I stumbled through the tangled spring growth). This hen was in a group of about five that crossed the road in front of us. I love her expression: Can’t a girl get some privacy around here?? Her “mohawk”, the line of feathers up the back of her head, distinguish her from an immature male yearling, or jake, which has a naked head.

Wild Turkey toms marching in formation
1/2500 sec. f/7.1 ISO 1600
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

And then, in a low pasture bordering the South Platte River, we spotted a group of at least seven hens and toms (officially, a “rafter”). These two toms marched left and then right across the front of the rafter, easing the rest of the birds back away from us, staying shoulder-to-shoulder, herding the hens and other toms towards cottonwood cover at the river. Apparently, wild turkey breeding males pair up to form temporary partnerships with each other, helping each other win mates. Accounts vary regarding whether both toms mate with a hen, or whether only the dominant one does… but there are many observations of cooperating toms.

Small rafter of Wild Turkeys displaying
1/2500 sec. f/7.1 ISO 1600
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

At one point (far in the distance) four toms were displaying, their backsides to us in evident bravado. By the creamy borders on their tail feathers, these are in the Rocky Mountain group; other groups across the US have rusty or chestnut edges on their tail feathers. And speaking of tail feathers, I’d love to know the story behind that big gap in one tom’s fan.

Female American Kestrel with dinner
1/2500 sec. f/7.1 ISO 2500
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

Our last hurrah for this two-day excursion along the South Platte was an American Kestrel, bringing home a lizard for dinner. We saw both a male and a female; the mature male has gray upper wings and a rusty cap, while the female has brown and black checked upper wings and a solid gray head. Though we didn’t see the two birds together, we assumed they were a pair, because the female circled the area beyond the trees several times with her prey, apparently looking for a safe route to her mate (or perhaps to her nest) away from our prying eyes.

Male American Kestrel resting after dinner
1/2500 sec. f/7.1 ISO 2500
Nikon D850 with Nikkor 500mm f/5.6E PF ED VR

And here he sits, after either having shared or devoured dinner, but before cleaning his feet. Sharing food is one of the courtship rituals of these birds, though it is usually the male that brings food to the female. Of course, we don’t know what happened in the minutes before we came along – he could have caught the lizard and given it to his mate, who flew around with it getting her picture taken while he perched to rest. Certainly we found them in a prime nesting location; they nest in holes in dead trees made by other birds, and this stand of cottonwoods complete with dead trees would be perfect. These photos are heavily cropped… I estimate the female was around 100 feet away, and she was tiny in the viewfinder. But we were so excited to see her with her quarry, I had to share.

We closed our excursion along the “Prairie Oases” Colorado Birding Trail with complete satisfaction. We’d seen many birds and bird behaviors that were new to me, the weather had cooperated admirably, and I shared two great days out in the wilds with my sister. Can’t ask for more happiness than that!