When looking for butterflies in March and April, I often look for wet stains high on tree trunks. If sap is leaking often butterflies such as Mourning Cloaks, Commas and Compton Tortoiseshells will come by for a sip. On the last day of April in 2018, I spotted some Commas circling rapidly around a tree trunk so I stopped for a closer look.
At first I just noticed the butterflies in silhouette. They were lining up on the side of the trunk that I couldn’t see from either the Green Butterfly trail at Riverwood, or the access path to the parking lot. Normally, I try not to go off paths but this time, the temptation was too much for me. I stepped carefully from dead ash log to rock trying to minimize how much of the leaf litter I stepped on in case something young and tender was trying to sprout. I also picked up 3 beer cans as a penance. But I have to admit, I moved 3 metres off the path to see the back of the tree trunk.
I watched in amusement as two Eastern Commas landed at the same time and started jockeying for position. They flap their wings and push forward seeking the best place to sip walking almost over top of one another. 
Finally, one gave up and flew to sun itself on the ground for a few minutes before returning.
This Mourning Cloak preferred to sun on the trunk of the next tree rather than on the ground.
Butterflies: Beware the Birds!
This was the source of all the sweet goodness the flies, beetles and butterflies were enjoying: a row of Sapsucker holes.
When a Downy Woodpecker flew in, I thought the butterflies might be eaten before my eyes. They darted away unharmed. The bird didn’t seem to care: delicately, he began to sip sap himself.
It was like watching a child eating freezies: he would drink all of the liquid gathered at one hole, then move on to the next.
Do Downy Woodpeckers Drill Rows of Holes to Sip Sap?
While watching, I wondered whether the neat row of holes were drilled by a Sapsucker or whether the Downy had chiseled them himself.
According to an article called “The Other Sap Tappers” in Bird Watcher’s Digest, Downy Woodpeckers will sometimes damage trees deliberately to get sap. They don’t drill a straight series of deep holes, though. At most, they nick the bark and then come back to get the beads of sap. Based on the information in the article, I think these holes were made by a migrating Sapsucker and this Downy is just enjoying them.
Even Tiny Sap Drips Can Draw a Crowd
On an earlier trip to the park, I had found a Comma on the leaf litter sipping sap that had dripped from a branch above. When I checked the area again, I could hear a slow splatter and eventually figured out where it was coming from. Looking up at the branches above it, I found another Comma and a Mourning Cloak both taking advantage of the tiny gap in the bark. The way their wings look like dead leaves when they are closed was certainly providing them with a disguise as they hung from the twig. I had to angle around a few times to get any sign of the colours and pattern on the Eastern Comma.
See You Next Spring
I passed by this same tree a few times that day, hoping to see any other types of butterflies that might visit. Twice more, I saw the Woodpecker return to sip more sap. I never saw it snap at any of the flies or butterflies gathered on the sugary water but that doesn’t mean he didn’t have a snack and a drink.
Two days later, when I was next in the park, the holes were dry. I’ll be keeping an eye out next spring, though, for more non-feathered Sapsuckers.
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Have you watched the visitors at dripping spring sap? Please share your sightings with a comment.