By Birding News on February 27, 2019 10 Comments
Bald Eagle Trio Paired for Life?
© 2019 StewardsUMRR, JCWiFi.
Three bald eagles—two males and a female—are nesting amicably at the Upper Mississippi River National Wildlife Refuge near Fulton, Illinois—again. The three parents share incubation responsibilities for the eggs—three this year—as they have in previous years. Like their relationship, their history is complicated. Male Valor 1 was young when he was spotted at the nest site in 2012. He is presumed father of that year’s two eggs, but he wasn’t helpful at incubation or feeding the young, and both eaglets died. In 2013, two males hung out at the nest, but Valor 2 apparently replaced Valor 1, and produced two young with female Hope. The next year, vegetation obscured the nest, but three adults appeared to be tending the young. In 2015, three adults were clearly seen tending the nest: Valor 1, Valor 2, and Hope. This was proving interesting, so Stewards of the Upper Mississippi River Refuge installed a nest camera, and in 2016, it was clearly documented that both males were copulating with Hope, and all three shared in incubation, nest maintenance, and feeding the young. Three eaglets fledged that year. But disaster struck in 2017: After two eggs hatched, two “foreign” adult bald eagles attacked the nest repeatedly for several consecutive days. Valor 1 and Valor 2 defended the nest, but Hope disappeared, never to return. Both dads raised the two eaglets to fledging. That September, a new young female turned up at the nest, and both Valor 1 and Valor 2 courted her. She laid two eggs in 2018, and all three adults tended them. Only one eaglet fledged, and the new female was named Starr. In 2019, she and her mates produced three eggs between February 18 and 24.
Bald eagles are normally monogamous for life, and highly territorial. These males have proven faithful to their nest—or to each other?—despite the loss of their mate.
Many bird species, including bluebirds and scrub jays, famously employ nest helpers. Usually such helpers are the unmated young of the previous year. Several bird species, most notably phalaropes, are polyandrous, in which a female has several male partners during a breeding season, and leaves incubation and care of the young to her mate. A nesting trio is a rare occurrence among bald eagles, but this is not the first such case. Bald eagle nesting trios have been documented in Alaska in 1977; in Minnesota in 1983; in California in 1992; and a few others. In those cases, though, it was not clear which or how many eagles were actual parents, and the third eagle was termed a “helper” for its role in incubating and feeding young. In the current situation in Illinois, it is clear that those eggs have two fathers, which may be unique.
