From Drought to Floods, Great Blue Heron Colony on the Rise

By Guest Blogger Jackie Vargo

I’ve been a citizen scientist for SFBBO’s Colonial Waterbird Program since 2014 and monitor a colony of Great Blue Herons that nest at Coyote Ranch Road in San Jose. Over the past four years I’ve noticed that weather has impacted my colony, but I am happy to report that this year my Great Blues are on the rise!
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In 2013, there had only been  4 nests, 3 adults, and 3 young in the Fremont Cottonwoods where they liked to nest. The year I started volunteering I observed that the small canyon below the land where Fremont Cottonwoods stood was mostly dry, ​as was much of the ...

nearby Coyote Creek, with the exception of a small pond. At that point the San Jose drought was in full swing, so having any water there was a blessing!
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Over the next couple years my colony’s population had its highs and lows, but the low point was reached in 2016, when there was only a maximum of 3 nests and 2 young seen at one time.  While it is possible that nests and birds were hidden in the dense Fremont Cottonwood foliage, there was minimal chick “cackling” or flying adults. It almost seemed as if my colony was not going to last another year.  

Miraculously, though, the torrential rains in 2017 helped the colony survive and the two Fremont Cottonwoods near Coyote Ranch Road and the Coyote Creek Trail slowly started to be the “place to be” for Great Blue Herons. I even saw a Great Egret nest with 3 egrets, although it didn’t last very long.

This year the canyon below the Fremont Cottonwoods is completely filled with water, and at some points the Coyote Creek trail was even flooded. On June 1st the colony boasted 14 nests, with 12 young and 14 adults, the highest number of nests and birds since before 2012!   
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Monitoring so many nests is fun because I get to watch the Great Blue Herons’ behavior. There is plenty of time to watch in awe as the parents fly up to the cackling juveniles and just stand there and take it as the kids fight over who gets to bug them for food first. The parents are so admirably patient! And as I wait with my scope pointed at the nest to see if there is actually another chick hiding low, I have to be patient too. It’s definitely worth the wait. 

You can learn more about our Colonial Waterbird Program on our website.    ​​