June 20, 2014 – Green Heron Nest Survey


Dredge and Rainey Report
Green Heron Nest Survey

June 20, 2014

Summary of accomplishments:

  • No dredging
  • Green Heron nest survey
  • unexpected predator revealed by trail cam

Green Herons are well known by the public at large, and are spoken of fondly by those that are familiar with them. The personable birds prefer to fish from overhanging branches and piers rather than wading like many other herons, and are known to use twigs or food as bait to attract minnows. Though well known, they are overlooked in the details of their life cycle, and their population has slowly been decreasing nationwide. Not much is known about their secretive nesting habits or nesting success. Timmy Vincent, the Senior Sanctuary Manager at the Paul J Rainey Wildlife Sanctuary, has watched them for years, and recognizing that we had a large population of nesting birds on the Refuge, interested Erik Johnson, our Director of Bird Conservation, into taking the species on as a special project. This is the second breeding season that we have sought out nests to band chicks, trying to unravel the mystery behind their population dynamics.

The July/August issue of Audubon magazine has a special feature on this project:  http://www.audubonmagazine.org/articles/birds/alien-landing

A video of a Green Heron hatchling can be accessed at http://youtu.be/d5H0cjaCUIY

To download a pdf of this report, click here: 

 

Tuesday, June17, 2014

Erik Johnson, Molly Folkerts and I met at the usual boat landing at 10:30AM and arrived at the Rainey headquarters to eat an early lunch. Timmy was out on the far reaches of the property clearing brush and grass from water control structures to protect them from lightening fires, but returned with a broken weed-eater while we were preparing to start our Green Heron nest survey.

Since the water level was high, we decided to start at Deep Lake Canal, which is a very shallow waterway that requires relatively high water to access. Timmy decided to come with us to see the new nest area we had discovered at the end of the canal, and to look at the small boat we had found last time that must have been left behind by a hurricane. The day started our survey out on a good note, since we were able to locate surviving chicks and new nests with eggs. This season has been shaping up to have a rather disappointing nesting-success rate.

Figure 1. A bucket of Green Heron siblings shows the range of sizes that are often found in one nest.

Figure 2. Erik and Molly banding chicks.

We finished nests along the northern canals and waterways and returned to the house to drop Timmy off. We still had high water, which meant we needed to do some of the other shallow canals at the south end of the property, so targeted Bob Gil Canal and the Safari trail. It was near 5:30 before we finished that stretch, so headed back to the house instead of starting another waterway.

Wednesday, June 18, 2014

Figure 3. Dawn for June 18, 2014.

The day dawned warm and muggy, and we did our best to get an early morning start. We were in the boat and headed out to the west side of our study area by 7:30, ready for a long, hot day. We started at “Timmy’s Corner” with a few chicks and new nests, followed by a tour of the McIlhenny Canals and Big Chick Canal. We finally encountered a few nests with banded chicks that had survived the passing two weeks. With so few chicks to band, we were finished early and tied up to a McIlhenny dock to eat a late lunch.

Figure 4. A week-old chick sporting the newest fashion in Heron jewelry, and starting to show more color in the face and wings.

On the way back, we unexpectedly found another nest on the main canal. Green Herons tend to favor the smaller, less traffic waterways, or cuts off of main channels. This one was right on a main thouroughfare. The parent bird did not flush even though we approached within 10-ft. It made us wonder how many nests we miss because of these more tenacious, “stick-tight” moms.

Figure 5. This parent refused to leave her newly hatched chicks, so we left as soon as Erik got a peek at what was there.

With time left in our day, we headed back to the southeast end of Rainey to search nests along Boundary and Sagrera Access canals, again with mixed success. Everyone was lost in thought on the cruise north and we completely bypassed Bruner Canal. Instead, we finished off south and north Goose Pond canals before heading back to HQ.

Relaxing at the air-conditioned headquarters, we watched the day fade as one of our deer and her fawn cautiously cross the yard.

Figure 6. Our resident deer cautiously cross the yard behind the house, keeping a close eye on our movements.

 

Thursday, June 19, 2014

Timmy headed out early to the boat landing to pick up a grad student that is working on shrimp and crabs in different types of submerged aquatic vegetation. It was a clear morning with a half-moon decorating the sky. We made a run to the dredge to pick up my minnow net, and passed Timmy returning.

We surveyed for GRHE nests down Last Point and Bruner canals. Erik took down 2 cameras on nests that had failed, and switched out memory cards and batteries. He then chose another nest with newly hatching chicks, and put both cameras up for a nest view and bush view to try to capture reasons for our seemingly high rates of nest failure, including predation. A large gator was cruising the canal, and we have found on more than one occasion that a gator would be intensely watching a nest area. We have speculated on possible predators such as gators, raccoons, snakes, Great-horned Owls, night-herons and rats, but haven’t had any positive proof.

Figure 7. A newly hatched green heron barely ahead of another one just starting to peck its way out of the shell. This nest will have two cameras on it to watch development and nest activities, and to attempt to catch what happens if eggs or chicks disappear.

Figure 8. Two cameras (red arrows) were placed on one nest (white arrow) to capture the nest area and bush area to capture what might be affecting nest success.

Figure 9. A nine foot alligator was cruising the nest canal, leading us to believe it might be looking for low-hanging nests.

We finished all of our planned routes by lunch. Erik finally had time to download the pictures captured by the trail cams from failed nests, and we were all shocked and surprised when one of them showed predation by a bobcat. How it made it to the nest through the long spikes and spines of the water locust tree is a real mystery. Now we are wondering if the levee along which these nest bushes grow, is a conduit for bobcat predation.

Figure 10. Motion triggered bird cameras placed over a nest revealed predation from an unanticipated source - a bobcat. It also captured a rat investigating the nest 6 hours later.

Erik and Molly were packing up to leave when Timmy mentioned all of the herons he had seen yesterday when taking the grad student along Tom’s Bayou. Tom’s Bayou is a natural waterway on the eastern side of the Rainey Sanctuary, and we had surveyed it last year. Erik had thought focusing on the core canals would keep our small crew busy, but with the low nest success, it wouldn’t hurt to go look. We found another 20 nests and banded several chicks. Comparisons of nest success will now be made between canal/levee nests and natural waterway nests.

With a more encouraging end to this nest survey, I took Molly and Erik back to the dock at 5:30.

Figure 11. A heron chick is next in line for a band while its anxious parent looks on from a nearby shrub.

Figure 12. Erik, Molly and Timmy inspect every bush for a nest.

Figure 13. The well-managed Rainey marshes are beautiful in the interior areas. Nest shrubs thin out where the natural stream bank is too low.

 

Friday, June 20, 2014

I prefer not to tow the boat late and when I’m tired, so stayed another night. I cleaned up after our group and left the Rainey headquarters when Timmy did at 8:30. There was a fishing rodeo this weekend at the boat launch, but luckily I came in during the mid-morning slow period and had no trouble loading the boat.

Figure 14. Dawn on June 20, 2014.

 

 

Karen A Westphal and Timmy J Vincent, National Audubon Society
Audubon Louisiana and the Paul J Rainey Wildlife Refuge
6160 Perkins Road, Suite 215, Baton Rouge, LA 70808
225-768-0921x202 office, kwestphal@audubon.org
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