As we near the end of my photograph queue, we have a contribution from ecologist Susan Harrison of the University of California at Davis. Her captions and narrative are indented, and you can enlarge the photos by clicking on them.
Birds on Non-Native (Alien, Invasive, Exotic….) Plants
Non-native species, usually ones introduced from other continents, are often called one of the worst threats to biodiversity, along with habitat loss, overexploitation, and climate change. We all know of terrible examples – kudzu, “the plant that ate the South”; mammal-swallowing Burmese pythons in the Everglades; the grasses that fueled the Maui fires. There’s a long list of ecologically devastating non-native species (here are 100 of the worst ).
Some conservationists argue that we should make peace with many non-native species and appreciate any benefits conferred by them. Other commentators go further and charge that opposition to non-native species is nothing but xenophobia (a hotly contested viewpoint). My one concession to this debate has been to shift to more neutral words (introduced, non-native) instead of potentially loaded ones (alien, exotic, invasive).
Birdwatching has sneakily softened my negativity toward non-native plants, however. One recent instance of this involved Sage Thrashers (Oreoscoptes montanus), a jauntily striped, melodious resident of the Great Basin sagebrush country that has been scarce and evasive in my experience. What a surprise it was to see veritable flocks of Sage Thrashers at Malheur National Wildlife Refuge, preparing for fall migration by gorging on berries of Russian Olive (Elaeagnus angustifolia) — one of the most hated non-native plants in U.S. deserts. In a five-day period, I never saw these birds eating anything else.
Here are some Sage Thrashers eating Russian Olives:
You can readily get Californians arguing over “the great Eucalyptus debate” – whether these towering and widely-planted Australian trees should be protected or eradicated. Our riparian bird hotspots in Davis, California have Eucalyptus (mostly River Red Gum, Eucalyptus camaldulensis) mixed in with the native Valley Oaks (Quercus lobata), California Walnut (Juglans californica) and other trees. It’s been a surprise to me how much native birds use Eucalyptus.
Black-headed Grosbeaks (Pheucticus melanocephalus), Bullock’s Orioles (Icterus bullocki), Western Tanagers (Piranga ludoviciana), and various warblers feed on lerp psyllids (Glycaspis brimblecombei), sap-sucking insects that arrived here from Australia in 1998. Red-breasted Sapsuckers (Sphyrapicus ruber) skip the lerp psyllids and feed directly on Eucalyptus sap after drilling into the trunk. The height of Eucalyptus trees makes them favored nest sites for raptors such as Great Horned Owls (Bubo virginianus).
Black-Headed Grosbeak on Eucalpytus:
Red-breasted Sapsucker on Eucalpytus:
Eucalyptus with lerp psyllids on leaves and sapsucker damage on trunk:
Great Horned Owl nest with nestling:
Here are birds using some other much-despised non-native plants at the local creek:
At home, while I’ll continue dutifully planting the yard with natives, I confess to sometimes envying the abundance of birds on the neighbors’ ornamental plants.