Bill Kaempfer mentioned checking hackberries on his recent CFO/Boulder Bird Club field trip to NE Colorado. As you may know, hackberry insects and birds/squirrel activity related to them is one of my mini-hobbies (i.e., some people are easily amused). In the last issue of Colorado Birds we talked about hackberry gall-making psyllids, of which there are at least 4 types in Colorado. The two most common ones in planted Northern Hackberry are the nipplegall and the blistergall. The nipplegalls present themselves are big bumps on the undersides of leaves, very evident at this time of year. The blistergalls are either dark green or purplish-black blotches on the leaves. Sometimes both types of galls appear on the same leaf.
Today on one of my regular visits to Grandview Cemetery, I noticed both Fox Squirrel and Black-capped Chickadee activity involving predation on developing psyllid nymphs within galls. The activities of both predators results in premature leaf drop of hackberry leaves under hackberry trees. When I looked at these leaves, there were two things going on. The tops of the nipplegalls were either bitten off or there were little peck holes in the blisters. Squirrels were doing the former, chickadees the latter. In the past I have also seen a variation on the theme by chickadees that involves their pulling a leaf from its branch, placing it atop a fairly big branch and standing on the leaf with each foot on opposite outside edges, and then wailing thru the heart of blisters with their beak. If you were to pick up such a leaf and hold it up to the light, you'd see holes precisely thru the middle of the blisters. If you think the holes form the pattern of the Big Dipper, I know you have a medical marijuana license. Other species I've seen remove psyllids from within galls include House Finches and Evening Grosbeaks. The REAL action involving migrant birds and hackberry comes when the nymphs developing within the galls reach adulthood and emerge to find overwintering sites in bark crevices on the host hackberry or any nearby tree. If the weather is right, this emergence can be compressed into a 1-2 week period and the trees are swarming with mini-morsals. Usually this occurs between mid-September and mid-October and benefits mid-to-late autumn migrating passerines. Connecticut and Golden-winged Warblers probably don't know what Colorado hackberry psyllids taste like, but Blackburnian, Yellow-throated, and Black-throated Greens and Blues do (along with kinglets, creepers, nuthatches, and many others). I would appreciate hearing about any observations related to hackberry psyllids and bird (or squirrel) predation. Thanks. Dave Leatherman -- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/cobirds?hl=en.
