Starling Deterrence – Horizontal Nest Box Use
By Cliff Brown

Background
In late 2004, after receiving approval from Chesapeake Farms, Dupont’s Kent Co. Conservation Easement, Agricultural and Wildlife Research property, it was explained during the initial field tour that starlings had completely overwhelmed the boxes situated in the primary wetland reservoir and duckling production was zero from 18 boxes.

All boxes were cleaned ahead of the 2005 nest season. It was hard to believe that they had been cleaned the prior year. Debris was over 18” thick in most boxes and many old eggs in layers were present. I thought this represented several years of unsuccessful nest attempts. Silly me.

Wood duck use (as subsequently determined by several interim nest checks that spring) was close to 300%!! At each nest attempt, ducks would lay several eggs and then starlings would enter and dominate. Routinely, after a starling hatch or while starlings were attempting to conclude their nest, other wood ducks would try to start another nest. The once cleaned 24” deep box would have a duck / starling “lasagna” – a stack of intermixed duck eggs, starling nest material, more eggs, more starling sticks, etc. but never a successful wood duck hatch. More than 600 eggs were thrown away.

Tactics
I had read from the Wood Duck Society newsletters how bad starlings could be. I had not experienced this problem in our private 4 year old program. I was amused to read about starling traps and other forms of harassment but nothing seemed very practical for a necessarily remote and passive deterrence technique. I recalled seeing reference to an old study where horizontal nest structures made out of 12” galvanized pipe had been successfully used. I then learned that Frank McGilvrey, retired USF&WS but still active as volunteer project manager at the Patuxent Wildlife Refuge, was one of the authors. I met Frank, got to observe horizontal boxes up close and immediately made and installed some either made from 12” x 24” sewer pipe (12” galvanized material was not available) or horizontal rectangles made by flipping several of the older wood boxes sideways and adjusting the openings.

Convinced that I could not do worse than zero ducklings, Chesapeake agreed that for the 2006 season, besides trying eight horizontal nests, we close the other vertical boxes in the reservoir in proximity to each other and add new boxes all along the woods-wetland margin surrounding most of the wetland. The concepts were to eliminate all starling housing, assuming the horizontals did their job, to offer wood ducks the woods’ margin boxes as an alternative house that would be less attractive to starlings as generally represented in other literature. Net capacity was temporarily reduced in this wetland but we had installed other new boxes elsewhere on the property and had hoped these actions might help their utilization. (It was over 90%).

Results
Three of the 8 horizontal boxes were used and hatched. Starlings did not enter any of them. Some starlings perched on the entrance on one horizontal long enough to “poop” extensively but never went in. The other woods’ margin boxes were almost all utilized and had either normal or relatively small dump nests. We opened 4 of the vertical boxes in late April. Two had successful wood duck hatches without starling interference and two were starling nests. All of the horizontal nests had been examined by wood ducks as rounded depressions in the nest material clearly indicated.

Perceptions thus far are that horizontal nests work and offer an excellent way to thwart starlings. Based on only one season’s observation, wood ducks do not seem to prefer these nests over vertical; however, in heavy use areas, they appear to use them readily. (3 other horizontal nests were installed in non-starling prone areas. The nest boxes were examined; one had a drop nest but none were successfully used).

Research will continue and expand in 2007. After the initial installation, I learned a few weeks later in the wooden horizontal boxes that we needed to make sure the back end of the horizontal nest was relatively dark to help entice woodies to use them. Our opening holes in the wooden horizontal boxes were also not 4” x 11” as recommended in the article which I also got belatedly. The wooden rectangle horizontal openings (4 of the 8) were roughly 6” x 8”. Nest use was split evenly between round sewer pipe and wooden horizontals. Thus, our quality control was lacking somewhat but we’re poised to rectify these minor aspects for next season.

It was also pointed out by Frank that he is fairly confident that it is the size of the entrance hole and not the amount of light allowed into the box that deters starlings. Patuxent Refuge continues to use horizontals as part of their housing mix and enjoys about 65% use on their 40 horizontal boxes without any starling issues.

The article is a must for anyone with starling issues and horizontals are worth trying:

A Starling-Deterrent Wood Duck Nest Box. Journal of Wildlife Management, Vol 35, No.4, October 1971 pp.793-797 by Frank McGilvrey and Francis Uhler.