Monday, April 25, 2016

Superb Day at Rocky Mountain Arsenal

April 24, 2016

Richard Stevens:

Rebecca Kosten and I drove to Rocky Mountain Arsenal (Adams County) for a day of birding and a picnic.  Temperatures reached the middle 60s; winds hovered around 9-11 mph.

Our first stop was the canal at 6th avenue & Potomac Street.  I had missed the Eastern Phoebe reported there for the past month on three previous trips.  Today it was flying around catching food along the canal, south of 6th avenue.

One mystery of why I kept missing the bird might have been solved.  We watched the flycatcher for 4-5 minutes.  Then it dove into an isolated bush and did not come out during the 15 minutes we continued to watch.  If I did not have photos, we would have thought the sighting was a ghost.

Next, we walked to Havana Ponds.  The prairie dog village along the trail was flooded.  A pair of American Avocets stood on a small island just offshore.  Two Killdeer walked to shore.

Havana Ponds had much water.  Unfortunately, the shore was quite weedy; there was no open "beach" for shorebirds.  Two American Pipits walked the rocky dam.

The highlight of the day was walking along the mudflats of the small "pond" below the Havana Ponds dam.  The lone shorebird here was a Short-billed Dowitcher "hendersoni"!

Field marks: rufous below with brown markings confined to spotting on undertail and sides of breast.  Unlike an alternate plumage Long-billed Dowitcher that would show spotted neck, spotted and barred breast, narrowly barred flanks.  Short-billed Dowitcher tail showed white bars equal or larger than black ones.  Long-billed Dowitcher shows dark bars broader than white ones.

When the Short-billed Dowitcher flew, the calls were "tu tu tu "much lower than the high pitched "keek" of a Long-billed Dowitcher.

Leaves were just opening on the cottonwoods along the Rod & Gun Club trail.  Four Yellow-rumped Warblers were the only warblers of the day.  A few White-crowned Sparrows and a Song Sparrow sang as we hiked to the Pond.

A lone sparrow in the grassy area caught our attention.  A rather drab bird with a dark lateral throat stripe, I first thought was an out of place Swamp Sparrow.  Except the stripe was not as dark as expected on a Swamp Sparrow.

We watched the sparrow for 20 minutes or so and observed the finely streaked crown, indistinct supercilium, spotted back, small bill and longish rounded tail of a Cassin's Sparrow.

We returned to the canal at sixth & Potomac in an attempt to get a better than witness photo of the Eastern Phoebe.  This time the bird was catching insects just north of 6th avenue.

I captured several photos and notice movement higher up in the cottonwoods.  It was a second Eastern Phoebe.  A pair, which may explain why they have been around for most of April.  Perhaps they are or will nest in the area?

Lower Derby Lake and Lake Ladora had few birds on them today.  We drove the Bison enclosure on the way out.  No Sage Thrashers or other uncommon birds were found.

A walk along the Legacy Trail added one Barn Owl and two Long-eared Owls to our fantastic birding day!

Raptors spotted today included a couple of Red-tailed Hawks, two Swainson's Hawks and a male American Kestrel with a prize (mouse) in its claws.

Our seven hour day at Rocky Mountain Arsenal was extremely enjoyable!

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