Andrenid bees at the FWG

by Christine Hanrahan

Originally posted in May 2011

About 5 years ago, I discovered an aggregation of Andrenid bees nesting on the north slope of the Amphibian Pond. At that time they were in one location only. The next year I went back to the pond in early spring, hoping to find them. It wasn’t until late April that they appeared, in the same location, at the time a nearby willow was in flower. Eventually, I discovered that they were Andrena dunningi, a species known to time its emergence to coincide with the flowering of willow trees.

Andrenid bee. These bees were very active in early afternoon under a warm, sunny sky. I would guesstimate about 30-40 were seen, fewer than the number of nest holes.

Over the next few years, I found them mostly in the initial location, but in 2007, I also found some nesting in another section of the north slope, where an abundance of non-native plants, mostly mustards and Chenopodium species, were growing (for that one year). The nesting, of course, took place before these plants had grown to full height.

This year, 2011, the bees were first noticed in late April, and, interestingly, I saw they had spread from their original site to the upper section of the track around the pond (not the Bill Holland Trail, but the “informal” track that was created when the bridge was closed last year), and to the west side of this track. I counted about 30 entrance holes at that point.

Constant foot traffic on the track meant that the burrows were continually being closed over, although new holes appeared regularly.

Andrenids prefer areas of bare soil with scattered vegetation, such as sparsely growing grass, and show a distinct preference for the tops of slopes. Their burrows are about 4-6 inches in length, as best as I can determine, so we don’t want to plant species with deep spreading roots that might prevent them from burrowing. Reading I have done since last week indicates that they will nest under exposed tree roots, but they are much happier with bare soil.

Some of the plants we have considered for this location (and we are not restricting the list to native only) include clover, grasses and sedges that form clumps (such as poverty oat grass and peduncled sedge), and possibly vines that will grow down the slope such as wild grape or virginia creeper.

Freshly dug nest site: you can see the mound of soil around the hole.

Andrenid nest entrance. Freshly dug holes often have a mound of soil around them (see photo above), but rain washes this away. Many of the nest holes are not apparent at first, especially if not surrounded by a mound of soil. They are also very small, approx. 1/4 inch or less.

NOTE: As of May 2017, we have found at least 7 species of Andrenid bees at the FWG: Andrena cressonii, A. dunningi, A. miserabilis, A. nasonii, A rufosignata, A. vicina, and A. wilkella (the last one is the only non-native). In addition to this location next to the pond, we’ve also seen them in the Old Woodlot.


Earth Day 2013 at FWG

by Christine Hanrahan

Happy Earth Day! It was a great day to be at the FWG, sunny, not too warm, not too cool, just right to bring out all sorts of wildlife.

I saw four mourning cloaks today, three around the ash woods, one by the butterfly meadow.

Wood frogs were still calling from the pond, not in any great numbers, but it is encouraging that they are there and seemingly more frequent than in 2012.

No spring ephemerals yet in the woods, but by the end of the week, I bet they’ll be in bloom. This means that for the moment, there isn’t much nectar for insects, so the lone willow tree, covered with pollen-drenched catkins, is very important, and ditto for the few clumps of crocuses and scilla. There were many andrenid bees on the willow and in their several usual nesting spots. Honey bees were gathering pollen and buzzing around the tree were many of the bee mimicking hover fly, Eristalis.

Birds were numerous as well. A female red-winged blackbird was in the Backyard Garden; soon there will be a lot more and nest-making will commence around the pond. Also new (to me, this year) was a pair of brown-headed cowbirds. A great blue heron flew toward Dow’s Lake, and a turkey vulture circled over the red barn. The kestrel pair was very much in evidence. Anouk reported barn swallows near the locks, while tree swallows were swooping and calling constantly.

Many ruby-crowned kinglets were melodiously singing. Song sparrows were numerous. One was by the pond collecting cattail fluff for its nest. Speaking of nests, a black-capped chickadee pair was excavating a nest hole in a birch snag.

And speaking of snags, Diane found a red-breasted nuthatch excavating a hole in another snag (not birch). If this pair nests, it will be a first for the FWG and, in a way, unusual for this species, which typically nests in coniferous woods. At any rate, doesn’t this show the importance of standing dead trees, AKA snags?

I also saw a pair of red-breasted nuthatches today. One was busy excavating a cavity in a snag (this is surely the same one seen by Diane). I watched from a distance and was interested in how industrious the bird was. I could hear the quick tapping as it chipped away inside the dead tree. Every few minutes its head would peek out and wood chips would be deposited outside. Sometimes the nuthatch came out and sat on the snag, as if resting.

Let’s see, what else was seen or heard today? Dark-eyed juncos, mourning doves, common redpolls still around, lots of white-throated sparrows, a few crows, house finches, american goldfinches, american robins, cardinals, starlings, hairy and downy woodpeckers, northern flicker, and a mallard in the stream running through the ravine.

Diane has some excellent bird photos on the blog. Please check them out, because they are wonderful, especially the one of the golden-crowned kinglet (she saw 5 on Sunday). She also reports seeing a belted kingfisher fly across the garden that day, as well as a pine warbler.

At this time of year, every day brings new sightings, so get out there and look! Spring doesn’t last long in our part of the world, and soon it will be sweltering summer.

More photos on the April blog