Return?

Jean, who lives on Woodard Ave, reports that she was leaving the co-op on March 1 and saw 30 herons in the sky. They settled in trees at the end of Bowman Avenue, a few blocks from the location where they've nested in previous years.

Breeding season has commenced

According to the literature, the heron breeding season begins in mid-February. Amy Buckler, the city planner, reports that the developer has renewed his land use application since the original approval expired. The development still calls for 6 townhomes to be built on the site that has been cleared directly east of the rookery.

The status of the land the rookery actually sits on is unclear. It is still owned by an out-of-state owner, according to the county records (which Amy Buckler says are often need to be updated.) No for sale sign is posted there. Yet the fact that the developer considered expending the number of townhomes by utilizing this site suggests that it is up for grabs.

I posted the site plan for the town homes at right, with the other maps. If you click on it, it will enlarge.

Disturbance

Gretchen-the-biologist sent me a bulletin on herons a while ago. It's not for posting, because it was only a draft document ("Survey protocol for measuring reproductive productivity at Pacific GBH breeding colonies"), but I think it's okay for me to post this excerpt, because it is pertinent:

Colony response should be tested and recorded using Data Sheet #3 (Colony Disturbance Summary). The various responses by birds are as follows (record all responses that occur):

No response. Birds ignore the observer. They may stare and subsequently look elsewhere, as other activities occur in the colony.

Stare. Birds view is fixed on the observer. This is particularly noticed when birds peer over the nest at an observer in the colony.

Chortle or cluck. The first sign that birds are disturbed is a low nasal “cluck” (Vennesland 2000), or "chortle" (Moul 1990). This activity may be continuous or start and stop as movement of the researcher occurs.

Stand. Incubating birds rise off the nest, or move around in the nest.

Off nest. Birds leave the nest, but stay on a branch nearby.

Scream. After chortling, the next progression in vocal alarm is screaming. This is a very loud vocalization and usually occurs with, or immediately prior to, flushing. Researchers must never cause this disturbance as it shows extreme stress (such as during a successful predator attack).

Flush/Return. Birds fly away, typically as individuals, circle and return to the nest. Researchers must never cause this disturbance, as it can lead directly to colony abandonment.

Flush/Leave. Birds fly away as a group and do not return until observer leaves the colony. Researchers must never cause this disturbance, as it is likely to cause colony abandonment.

I'm not sure how researchers are to execute this test. When the leaves come down it'll be interesting to get the nest count.

Another conclusion

It is possible that it was the increase in human foot traffic that led to nest abandonment. This is partly the fault of the road, partly the fault of the web site.

So the creation of the web site could have had, all in all, a negative impact on the heron population. Would the road have been created so far ahead of construction had there not been signs that people were watching what happened to this parcel?

Closed for season

Breeding activity has concluded. I haven't seen herons at the site for at least a week.

Here is my strictly non-scientific assessment of what happened this year, post-road right-of-way. Initially there seemed to be an increase in heron activity, with new nest construction. Some of the nests, however, were abandoned early on--I'm not sure whether before or after eggs were hatched.

Still, I heard and saw a lot of post hatching activity. Later in the season, though, there appeared to be abandonment of nests, perhaps due to eagle predation as described by Susan.

My theory is that the road provided improved access, for herons and for eagles. This lead to the increase in nest-building activity and the subsequent abandonment of nests, as eagles started feeding on young birds. It will be interesting to get the nest count once the leaves have fallen. But this will not tell us how many of those nests successfully fledged chicks. Toward the end of the season I was only hearing/seeing birds at two nests.

Number of fledglings?

It seems that the number of young herons present at the rookery has dropped. So I asked Susan, who lives a block away, for this first-hand account:

"On July 11th my brother and niece came to visit. We decided to walk over to the heron rookery just around the corner from my house. Sierra had never seen anything like it before and was excited to see a heron way up in the alders and maples. It was a little hard for her to see them so high above. Along the dirt road near the open clearing we discovered grey feathers, feet and a beak; the remnants of an unlucky heron that had been a predator's meal. Then, as we were peering into the trees to see the wide gray areas on the ground as clues to which trees have nests, we spotted a heron standing on the ground. What a discovery for an 8 year old! It was staying very still, probably trying not to be noticed. We started speculating as to what it might be doing. Could it have survived a fall from the nest? Possibly. Did it land and walk down there on purpose? It didn't seem likely. We had questions. Would it learn to fly? Was there enough room between the trees for those big wings to spread out? How long had it been there? Was it hungry? We wondered if it needed some urging to get out in the open where it might be possible for it to try flying. We decided to go into the woods to get a better look, even with the risk of being covered in those fishy smelling gray droppings that cover the ground under each nest. We didn't get too close to the heron, but we made our way through ivy and fallen limbs past the heron. It certainly watched us and started to move away if it felt we were headed towards it. Once we were past, we started moving in its direction to herd it out to the cleared area next to the rookery. Watching those long legs from 20 to 30 feet away was amazing. They have an awkward grace when on the ground. At one point the bird opened its wings and lifted about a foot off the ground, but went back to walking. Once it was out in the open we stopped to see what it would do. It moved away from us in the open, then went back into the cover of the trees. Oh, well. I guess it wasn't going to fly that day. We went home. There, a neighbor showed us the heron shells she had collected under the nests when the chicks were hatching as the pieces were kicked out of the nest. They are a light blue and seemed to be just slightly larger than a chicken egg. We all wondered about that heron for the next week. How was it doing? Would it survive? The next Saturday, July 18th, my brother's whole family came for a visit. Both my nieces this time. We walked to the rookery to see if our grounded heron was still there. We didn't see it. Jessica was disappointed that she didn't get to see it after listening to Sierra's stories all week long. We did see some herons in their nests in the trees. We got to hear their odd, prehistoric sounding calls. We talked about the predators that they have to contend with. From the sky they are attacked by eagles, hawks, and at night, owls. From the ground there are raccoons. As we walked further along the dirt road Sierra noticed something out in the open clearing, "Look! I think something got a heron!" She was right. Up ahead we could see the blue feathers and something bright red. We wondered if it had been our heron in the woods from last week. The girls wanted to see it, even though it might 'gross them out.' Most of the bird was eaten, just feathers, feet, head, beak, and a little muscle tissue still attached to some bones remained. We could tell that this happened just recently. The muscle tissue wasn't even dried out. We had heard quite a ruckus from while still at my house a little earlier that same afternoon. We decided that was probably when the attack occurred. We all felt sad for the herons, but we knew that what ever ate it (possibly an eagle) probably had young to feed, too. Living a block away from a heron rookery can be quite loud at times. As I learn more about them I can predict what may be occurring as I hear the varuous sounds from my backyard. Early in the breeding season I see herons landing in the fir trees near my house to pick out branches an twigs for nest building. When they fly in low it seems I can almost feel the wind move as they beat their huge wings. After a few weeks we start to hear a sound like ducks quacking and we know that the chicks are starting to hatch. When it sounds like a lot of ducks are talking all at once we think a parent must be approaching with food. As the weeks continue to pass the quacking sound becomes more prehistoric sounding. (I like to pretend I live in "Land of the Lost" with pteradactyls flying over regularly.) Every few days I hear all the herons start making noise at once. It can be quite loud and any time of the day or night. I now know that indicates a predator attacking. Luckily the population seems to grow inspite of the predators. About 5 years ago when we moved to this house there was only a couple of nests. Now the trees are full of them."

End?

I went to view the rookery yesterday at four pm. Saw one heron on a nest and heard another vocalizing, but was surprised by the overall lack of activity; did not see any herons fly in or out.

Not sure what this means. Last year the young fledged right before the mid-August "official" end of the breeding season (i.e. when construction can begin).

My first thought was that the warm weather had sped up the season.