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Introduction | Methodology | Results | Recommendations | Literature Cited

Introduction
The presence of various bird species in Cuyahoga Valley National Park (CVNP) has been documented for many years. However, this data has been limited to simple records of species sightings. In the past, there has been no attempt to monitor population trends which could serve as an indicator of the overall health of an ecosystem. In an attempt to collect detailed information about specific birds, the Resources Management Staff began a survey of Great Blue Herons (Ardea herodias) in the spring of 1993.

Herons are intimately linked and dependent upon the quality of their habitats, making them excellent indicators of ecosystem health or decline. Nests may be found adjacent to lakes, rivers, and wetland marshes, although inland herons can also be found several miles away from water. Food sources for herons include fish, crayfish, frogs, snakes, snails, small rodents and insects (McShane, 1995).

This survey was designed to monitor nesting sites of Great Blue Herons and collect information which would document numbers of nesting pairs, reproductive success and geographic distribution. This 1997 report summarizes the fifth year of this survey.

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Methodology
All previously known and newly reported nesting sites were investigated by a Resources Management staff person or volunteer to verify nesting activity. Each tree containing an active nest was tagged with an unique number and the following information was collected:

-exact site location, using global positioning system if possible,

-description of site (vegetation cover type, slope and aspect),

-tree species, DBH and height,

-dates of site visits,

-dates of construction of nest, occupancy, incubation, and hatching were recorded,

-number of young fledged.

Active sites were visited on a weekly basis to record changes in activity. Nests that showed no sign of occupancy were visited less often throughout the nesting season to check for any late occupancy.

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Results
It was known in 1993 that three Great Blue Heron nesting areas existed in or near CVNP. One of the heronries is located on Cleveland Metroparks property in the Pinery Narrows area. This site is located along the west side of the Cuyahoga River about 2,000 feet north of the Station Road Day Use Area. Except during extreme drought conditions, the trees in this heronry are surrounded by water. A canoe was used to enter the area in 1993 for the purpose of tagging all the trees that contained nests and collecting data. This heronry has not been monitored since 1993 due to lack of personnel. Also, the heavy vegetation between the railroad tracks and the heronry made accurate monitoring of the site difficult.

The remaining two heronries are on property owned by the Akron Water Pollution Control Station. Permission was obtained to access this facility on a weekly basis. The first heronry in the facility is located south of tract 116-57 and Bath Road and east of Akron-Peninsula Road. The site is at the edge of an old settling pond. Observations were made from across the pond using binoculars and a spotting scope.

The second heronry is located in the treatment plant, south of Bath Road between Riverview and Akron-Peninsula Roads on the east side of the Cuyahoga River. This road receives heavy traffic throughout the day, and now has a roadside pullout built for viewing the birds.

Observations of the heronries began as early as February 12th, with nest construction. Occupancy of the nests began around March 14th, with incubation by March 29th. Chicks were noticed as early as mid May and fledging of the young completed by early August.

Figures 1 and 2 compare the number of young and the number of active nests at each of the heronries from 1993  through 1997.  This link contains a chart in Adobe Acrobat format (pdf). Acrobat Reader is available free online.

The number of active nests at the Upper Lagoon decreased dramatically because of high winds in late February that toppled the tree limbs containing the nests.

The number of active nests and number of young at the Bath Road heronry has decreased from 1996 to 1997. While 123 chicks were initially observed to have hatched, only 116 (94%) of those chicks were observed fledging successfully. Seven of the fledglings were observed to have disappeared prior to being of flight age. This was most likely due to predation by other animals. It is possible that the observer made an error, or the birds did not survive due to predation or falling from the nest.

Although adult herons have few natural predators, fledglings and young herons are preyed upon by raccoons, hawks, snakes, owls, vultures, and crows. Starvation and exposure also take their toll on young herons (McShane, 1995).

In 1992 and 1993, Ms. Becky Carlson, Professor of Biology at John Carroll University, surveyed and found seven nest sites within the Cuyahoga watershed. Most colonies were of recent origin indicating an increase in heron populations. The oldest site, established in 1958 near Tinkers Creek in Solon is experiencing a sharp decline. This decline is due to encroachment of a large housing development on the heronry's perimeter. Carlson notes that colonies can be found near populated areas as long as habitat and prey are available and the herons and their young are not stressed by physical disturbances.

Population Trends of Breeding Birds of Ohio (Earnst & Andres, 1996), summarizes breeding bird survey data from 1966 through 1994. This report suggests that Great Blue Herons increased significantly in Ohio at 5.6% annually. Surveys suggest that the inland heronries are growing more rapidly than those along Lake Erie. The continental and Great Lakes Regional population trends also increased significantly at 3.0% and 4.3% annually. The Breeding Bird Survey (BBS) also lists the Great Blue Heron as a species that is significantly increasing in Ohio.

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Recommendations
The data collected since 1993 has provided significant baseline information necessary for the ongoing monitoring of the Great Blue heron in Cuyahoga Valley. Monitoring of the heronries should continue next year. Due to limitations in staff resources we will continue to utilize volunteers. The entire monitoring project this year was completed by volunteer staff contributing over 22 hours of observational data.

Literature Cited
Earnst, S.L. and B.A. Andres, 1996. Population Trends of Breeding Birds in Ohio. Ohio Biological Survey, Columbus, Ohio.

McShane, Laura. 1995. The Rap Up. Cuyahoga River Community Planning Organization

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