Over the last three days Paul Slingsby and I monitored colonial waterbirds at several locations in North Park. During stop at the Arapaho National Wildlife Refuge Headquarters, a member of the refuge staff (now reduced to two people) mentioned that birders have been asking when the grebes will have young on their backs. The answer to that question varies with grebe species and location.
Western Grebe: We found breeding Western Grebes at Walden Reservoir and Lake John. (this species does not generally breed on the ponds on the refuge tour route.) At Walden Reservoir, we counted 243 Western Grebes (51 young and 192 adults). Many of the adults were accompanied by young, some on the backs of adults, and some swimming with adults. At Lake John, nesting appears to be less advanced than at Walden Reservoir. Located in rushes at the northwest corner of the lake, the colony here usually has more than 20 pair nesting. On Thursday, we found only 4 nests visible in the rushes. Unusual, were three nests anchored in smartweed. This species almost always builds nest in the shelter of cattails or rushes in North Park. Adult grebes swimming in the vicinity of the rushes did not appear to have young.
Eared Grebes: These grebes tend to be later nesters in North Park, though they may begin courtship and make nest building attempts shortly after arrival. In some situations, they build nests in cattails or rushes like the Western Grebes. Often in North Park, however, they nest in open water with nests anchored in smartweed or other aquatic vegetation. Water levels are often high on reservoirs early in the season frustrating construction of nests in open water. In addition, the aquatic vegetation does not become available until later in the season. Early nesting attempts in open water are also often frustrated by changing water levels, particularly when drawdowns for irrigation drop leaving nests exposed. At Walden Reservoir on Thursday, we counted 1337 Eared Grebes over the entire reservoir; there were no young evident. Many were paired, and there was courtship. At a narrow neck of the reservoir, we found about 134 nests in a large area of smartweed. Birds were on some nests and building others. Eggs were visible on two nests. On this reservoir, the Eared Grebes have also historically nested in the cattails and rushes around the perimeter of a large island. On Thursday, we saw no grebes near this island and did not hear the calls usually associated with a colony. Eared Grebes may have young here in a couple of weeks, though adverse weather could delay production. At 18 Island Reservoir, another excellent spot for observing Eared Grebes, only a few birds had begun nest construction.
We did not visit the refuge tour route where there is often a small Eared Grebe colony.
If planning a visit to North Park this summer, it is advisable to check weather forecasts for wind directions. A major forest fire is burning in the northwest corner of Jackson County and may not be controlled until mid-October. We were lucky to have mainly winds from the south, so did not experience much smoke in the air. Winds from the northwest would diminish air quality. If you plan an overnight stay, it would be advisable to check for reservations ahead of time. Fire fighting support is adding to the pressure on North Park lodging caused by oil and gas activity as well as the usual summer tourist traffic.
Chuck Hundertmark
Lafayette, CO 303-604-0531
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