Dispersal of a Heron-Egret Rookery

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln

2 - Second Eastern Wildlife Damage Control Conference (1985) Eastern Wildlife Damage Control Conferences

September 1985

DISPERSAL OF A HERON-EGRET ROOKERY

Douglas I. Hall U.S. Fish and Wildlife Service

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Hall, Douglas I., "DISPERSAL OF A HERON-EGRET ROOKERY" (1985). 2 - Second Eastern Wildlife Damage Control Conference (1985). 21. https://digitalcommons.unl.edu/ewdcc2/21

This Article is brought to you for free and open access by the Eastern Wildlife Damage Control Conferences at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in 2 - Second Eastern Wildlife Damage Control Conference (1985) by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. DISPERSAL OF A HERON-EGRET ROOKERY habitat was primarily Eastern redcedar by Douglas I. Hall* with a few scattered deciduous trees adjacent to the small drain transecting ABSTRACT the site. A rookery composed of an estimated The birds had successfully reared 10,000 herons and egrets (family: Arde- young in this same location for two suc- idae) located in Van Buren, Crawford cessive years despite repeated, costly, County, Arkansas was successfully dis- ineffective dispersal attempts by resi- persed in the Spring of 1983. A diver- dents with the assistance of representa- sified scaring program was planned and tives of state, county and local agen- initiated prior to the onset of court- cies. With the approach of the nesting ship display and nest building. The season in 1983, city officials contacted roost relocation was subsequently fol- the U.S. Fish and Wildlife Service, lowed by habitat alteration procedures Wildlife Assistance Office, Stuttgart, to make the 5-acre stand of primarily Arkansas for help in preventing a recur- Eastern redcedar (Juniperus virginiana) rence of the problem. unattractive as a future roosting site. I want to extend my appreciation for Although no nesting occurred at the the outstanding cooperation received by site in 1983, the lack of an early sca- the city and county officials and pri- ring program in the Spring of 1984 re- vate citizens of the town of Van Buren sulted in the uncleared portion of the who participated in the relocation ef- area being used as a roost site. forts. Thanks also to Mr. Thurman Guidelines were established to deal Booth, State Supervisor, U.S. Fish and with future rookery problems. Wildlife Service, Little Rock, Arkansas for reviewing this paper. INTRODUCTION Heron-egret rookeries, not unlike METHODS large concentrations of roosting black- In March 1983 field observations of birds (Icteridae), can create social, the roost site revealed roosting activi- economic and health problems whenever a ty and courtship displays indicating rookery is established in a location that the birds were again planning to considered competitive to man's inter- use the same area as a rookery. Meet- est. Increasing numbers of problems ings were held with the landowner, May- with heron-egret rookeries are occur- or, County Agent, County Sanitarians, ring as the birds seek suitable nesting and the media to discuss management al- habitats in areas inhabited by man. ternatives. The plan for resolving the Such was the case starting in the problem was three-fold: (1) immediately Spring of 1981 in Van Buren, Arkansas. harass and disperse any birds display- A nesting grounds was chosen on an ap- ing or attempting to begin nest con- proximate 5-acre tract of residential struction utilizing a diversified scar- land located in the northeast section ing program; (2) mark the stand for of the town of Van Buren, Crawford habitat alteration procedures to begin County, Arkansas. as soon as possible; and (3) prevent The rookery was composed of an esti- the formation of another rookery in an mated 10,000 of the following species: unfavorable location. Cattle Egret (Bubulcus ibis), Great Eg- ret (Casmerodius albus), Snowy Egret RESULTS (Leucophoyx thula), Great Blue Heron Through an excellent program of (Ardea herodias), and Little Blue Heron inter-agency cooperation, landowner a- (Florida caerulea). The predominant greement and neighborhood involvement, species was the Cattle Egret. Nesting the birds attempting to roost at the site in April 1983 were dispersed with the following equipment: (1) pyrotech- *Wildlife Biologist - U.S. Fish and nics (shellcrackers and racket bombs); Wildlife Service, Wildl. Asst. Office, (2) 4 propane cannons; and (3) one P.O. Box 570, Stuttgart, AR 72160. pole-mounted 200 watt broadcast alarm unit. Dispersal involved less than 500 has been to recommend habitat modifica- rounds of pyrotechnics. Harassment was tion or a hazing program prior to nest- spaced out over a three-week period, ing or after the birds have migrated in primarily in the morning and evening the Fall. The nesting-parental instinct hours supplemented with intervals of is too strong to overcome with a scaring sound from the broadcast alarm unit and operation if undertaken when eggs or propane cannons during the middle of fledglings are present in a rookery. the day. The technique for dispersal Such was the case in 1982 in Van Buren was similar to that described by Mott and hence the operation failed. (1980) for blackbirds and starlings The nesting season of 1983 would have (Sturnus vulgaris). been the third consecutive year for the During this dispersal time, the accumulation of bird droppings at the stand was marked for habitat alteration rookery site. Thus, the potential would and arrangements were made for the have increased for the respiratory di- county-owned bulldozer to be used in sease histoplasmosis to occur because of the clearing operation. Nearly all ce- the establishment and proliferation of dars were removed from the 5-acre site the fungus (Histoplasma capsulatum) in and piled into the drainage ditch lo- the feces-enriched soil (Weeks 1984). cated on the area. Some sycamore (Pla- Other potential human health and safety tanus occidentalis), sweetgum (Liqiud- dangers associated with any bird colony ambar styraciflua), post oak (Quercus include the aggravation of other respi- stellata), and other hardwoods were ratory diseases and allergic reactions left along the small drainage. from the inhalation of dried feces dust The herons and egrets made several and bird dander. attempts to establish new roosts in and Urban rookeries are also objection- around the city. However, through good able because of the general noise, public awareness of the operation and filth, and odor accompanied with the the prompt reports of any new build-up accummulation of so many birds, their of birds in the area, we were able to droppings, dead young, broken eggs, and prevent another rookery from forming in regurgitated food. The build-up of Van Buren in 1983. However, the colony these by-products attract scavengers apparently reestablished approximately and rodents that can cause other prob- 13 miles west in the town of Muldrow, lems. Over-nitrification of the soil Oklahoma and successfully reared young. at a colony normally leads to the vege- In the Spring of 1984, the birds re- tation dying. These problems contrib- turned again to Muldrow where they were ute to the rapid decline in property met with an agressive scaring campaign. values and in some cases may prohibit (Peterson, B. personal communication, potential development of the property 28 April 1984, State Supervisor, U.S. unless the area undergoes the costly Fish and Wildlife Service, Oklahoma soil decontamination process to kill City, OK). The problem in Muldrow was fungal spores described by Weeks (1984). solved but presumably some of this same Because of the successful Van Buren re- colony returned to the remaining decid- location, the former rookery site is uous trees in the Van Buren roost that now targeted for residential develop- were not cleared in the habitat modifi- ment. cation procedures of 1983. These birds Economically, it is better to manage immediately began nesting, disallowing an urban rookery before it reaches the any harassment or further habitat al- critical stages. Cost estimates for teration until the Spring of 1985. the 1983 relocation operation was $2,000.00 and 170 man-hours based upon DISCUSSION estimates from city and county offi- Because of the sensitivity involved cials (Bell, G, May 1983, City Mayor, in the management of an aesthetically Van Buren, Arkansas). The cost is min- pleasing avian species such as herons imal compared to what could have resul- or egrets, the guidelines in Arkansas, ted with the loss of human health or as with other states in the Southeast, life, reduced property values, decontamination expenses and/or litigation — Request permission for habitat al- for an improper relocation effort. teration to be performed by neigh- To maximize cost effectiveness and borhood volunteers (chain saw work improve the efficacy of any dispersal parties, or larger equipment if program, it is desirable to have good necessary). inter-agency coordination, public sup- port and involvement. In Arkansas, it — Eliminate landowner liability is common practice to communicate with problems in the event of an ac- our cooperators a minimum of twice a cident. year to remind them of the services provided by the Wildlife Assistance — Assure that the job will be Program. In this manner, it is hoped done adequately and that the that early recognition of an attempted slash will be piled and burned. establishment of a colonial bird rookery in an unfavorable location will be — Stress increased property values possible and an effective management if habitat alteration is underta- plan can be formulated. ken, the roost site is eliminated In spite of the prior history of and the potential health hazard is rookeries in Van Buren, another urban removed. colony formed in April 1985 at a new location approximately one-half mile 2. Habitat alteration south of the former site. The birds began nesting and laying eggs before — Involve the media. You may have appropriate action could be taken. Any more success in reaching interes- habitat modification or harassment de- ted parties through a newsletter cision would have resulted in indirect or newspaper article than trying mortality to the juvenile birds and to get citizens to attend a meet- that would have been biologically and ing in February or March when the politically inappropriate. In 1985, problem has not yet occurred. the birds have fledged their young without any disturbance. — Obtain volunteers from the owners In an effort to prevent the heron- of surrounding property with em- egret rookery from establishing at the phasis on all citizens that have same location in 1986, a series of voiced complaints in the past. guidelines were prepared for the city officials to follow. With little modi- — Ask for a volunteer to head the fication, these procedures listed below neighborhood watch team. This in- will make the task of any rookery relo- dividual should be an interested cation less time-consuming on public person that can coordinate the ac- officials,, provide more neighborhood tivities of the group through the involvement, minimize human health and officials in charge of the opera- safety hazards and result in a success- tion. ful dispersal operation: — Establish work days for thinning, Recommended Guidelines for Heron-Egret piling the cut trees and burning Rookery Relocations the debris.

1. Obtain landowner permission — Service personnel should assist in marking and thinning the stand. — City, county and/or U.S. Fish and Wildlife Service personnel (Ser- 3. Roost relocation vice) meet with the landowner to explain the problems involved — Emphasize the need to report evi- with the roost remaining in the dence of the first birds to re- same location (i.e. health and turn to the area. safety aspects). — Begin the scaring operation when LITERATURE CITED the first birds arrive. This may only entail one propane cannon MOTT, D.F. 1980. Dispersing black- initially. birds and starlings from objection- able roost sites. Proc. 9th Vert. — If birds persist at the target Pest. Conf. 9:38-42. area or any other area that is undesirable as a rookery site, WEEKS, R.J. 1984. Histoplasmosis. set up one or more pole-mounted Sources of infection and methods of broadcast alarm units to play re- control. U.S. Dept. Health and Hu- corded distress calls at timed man Serv. Public Health Serv. CDC. intervals. The use of electronic Atlanta, Georgia. equipment will require responsi- ble citizen coordination.

— If necessary, implement a diversified dispersal operation. For this to be successful, it must be performed prior to nest building.

— The scaring program should be a joint effort of interested citizens, the Mayor, the County Sani- tarian, the County Extension Ser- vice, the City Police, the State Wildlife Agency, the Fish and Wildlife Service, and other appropriate agencies.

— A necessary portion of the dispersal process is preventing the birds from relocating at another undesirable location.

— Be sure to involve the media so the citizens will be aware of what is happening.

The successful dispersal of the Van Buren heron-egret rookery in 1983 was a product of excellent cooperator and community involvement. No one depart- ment or agency could have accomplished the operation as effectively. Because the colony relocated in subsequent years, it has strengthened the awareness of the expanding nature of this type of migratory bird problem and pre- cipitated the formulation of rookery relocation guidelines for future use. Operations of this nature help to en- hance the public awareness of the Fish and Wildlife Service.