Once again, our nesting colony of grebes at Lake Almanor has been abandoned due to a sudden, dramatic change in reservoir elevation, leaving nests along the shore. A total of 470 active nests were counted at Goose Bay on August 28, 2020 and by September 11, 2020 the whole colony was beached.

To recount, that's:
788 abandoned nests in 2016
1,205 abandoned nests in 2018
657 abandoned nests in 2019
470 abandoned nests in 2020
3,120 abandoned nests in the past five years, for a total of 9,320 lost bird years.

Overall, Western and Clark’s grebe (Aechmophorus occidentalis and A. clarkii, respectively) populations are declining on the Pacific (Wilson et al. 2013), which makes this large breeding population at Lake Almanor critical to recruitment for the species persistence in California.  Water management decisions likely caused low reproductive success for these species in 2002 and 2003 (Ivey, 2004) and again in 2010, 2016, and 2018 (Plumas Audubon Society). In 2019 and 2020, rapid water level drop rates contributed to complete abandonment of large breeding colonies and the resulting low productivity in those years, creating long-term impacts for the grebe populations. Cumulatively speaking, four of the past five generations of Lake Almanor’s Aechmophorus grebes have been impacted by decreasing breeding habitat availability, resulting a total loss of 3,120 abandoned nests in the past five years, or over 81% of all documented nest attempts. PG&E has worked with Audubon since 2018 to improve conditions for grebes and avoid unnecessary take of Aechmophorus grebe eggs during their breeding season at Lake Almanor but these objectives have not been attained.

In late July and early August 2019, a colony of nesting Western and Clark’s Grebes at the lake grew to a peak of 657 active nests, observed on July 31st, 2019. By August 1, 2019 the colony had largely been abandoned with many nests left stranded on land with extensive evidence of depredation present. By August 9th, 2018, there were no more active nests and Ring-billed Gulls were observed atop Aechmophorus grebe nests. The average adult population in 2019 was 3,797 adult grebes, while reproductive success was dismally low, at 0.0005. The reproductive success rate of 2019 is the single lowest reproductive success rate we’ve seen of all 10 breeding seasons studied at Lake Almanor, according to data collected by Plumas Audubon Society. 

This season was only fractionally less devastating. Western and Clark’s Grebes had a tremendous struggle setting up their colony during the 2020 breeding season.  Plumas Audubon Society members observed, the birds initially set up around 40 nests at Catfish Beach on July 20, 2020.  Later in the month on July 30, when Plumas Audubon Society staff returned to the colony site, 75 abandoned nests were observed at Catfish Beach and Pelican Island, while 97 active nests were observed in the Causeway colony site.  A follow up survey on August 8, 2020 found 244 abandoned nests in the Causeway colony site, 142 active nests near Chester Meadows, and 15 active nests near Pelican Island.  Aechmophorus grebes made a final colony attempt at Goose Bay in August, with a peak of 470 active nests and 1 chick observed at Goose Bay on August 28, 2020. Ultimately the birds experienced nearly complete reproductive failure again at Lake Almanor during the 2020 breeding season.  The estimated date of colony abandonment in 2020 is September 9, 2020.