Breeding colonial waterbirds are particularly susceptible to human disturbance because of their high-density nesting habtt~ Identified detriments to reproductive success include egg and nestling mortality, nest evao~tior~ reduced nestling body mass and slower growth, premature fledging and modified adult behaviorg Fifteen species of colonial waterbtrds nesttng at 17 colonies in north and central Florida were exposed to three different human disturbance mechanisms (HDMs) in order to determine recommended set-back (RS) distances for protecting these mixed-species nesting assemblage~ Both intraspeciflc and inter. specific variation were observed in flushing response distances to the same human disturbance mechani.¢mg In genera~ colonial waterbirds exhibited greater average flush distances in reaction to a walking approach than to approaching motor boat~ Recommended set-back distances were estimated using a formula based on the mean plus 1.6495 standard deviations of the observed flushing distances plus 40 meters ~S = exp (# + 1.64950 + 40)]. In genera~ a recommended set-back distance of about 100 meters for wading bird colonies and 180 meters for mixed tern~skimmer colonies should be adequate to effectively buffer the sites we studied from human disturbance caused by approach of pedestrians and motor boats. We recommend follow-up studies to test our model at other breeding colonies.Distancia de alejamiento para proteger de las perturbaciones humanas alas colonias de aves nidificadoras en Florida Resumen: Las ayes acu~ticas que habitan en colonias durante el pertodo de criag son particularmente susceptibles alas perturbaciones humanas por sus hdbitos conducentes a una alta demidad de nido~ Los factore$ que disrainuyen el dxito reproductivo, tncluyen ia mortaltdad del huevo y el ptch6r 6 la evacuaci6n del nid~ la reducci6n de la masa corporal del pich6n o crecimeiento lento, el abandono prematuro del ntdo por parte de los pie.hones y comportamtentos adultos modificados Quince especies de colonias de ave$ acu~ticas que nidtflcaron en 17 colontas del norte y centro de Floridg fueron expuestas a 3 mecanismos de perturbaci6n humana dtferenteg a los efectos de deterrainar distanctas de alejamtento recomendables para proteger las agregaciones mtxtas de dstas especie£ Variactones tntra-especificas e inter-especificas en ias distanctas de respuesta frente a los mismos mecanismos de perturbaci6n humana En genera~ los colonias de ayes acu~ttcas exhtbteron una mayor dtstancia promedio antes de volar en reacct6n a la cercania de pasos que al acercamiento de una embareactbn a motor. La dgstancia recomendada de alejamiento rue esttmada utilizando una f6rmul~ basada en la media md~ 1.6495 desvtaciones standard de la distancias antes de volar observad~ md$ 40 m ~RS = exp (# + 1. 64958 + 40)]. En genera~ una distancia de alejamiento de alrededor de 100 m para lus colontas de aves zancudas y 180 m para las colonias mtxtas ("tern/skimmer"), seria adecuada para amortiguar a los sitios que estudiamos de los tmpactos de las perturbaciones ...

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Outdoor recreation and ecotourism can have negative effects on wildlife species, so it is important to determine buffer zones within which activities near critical wildlife areas are limited. We exposed 23 species of waterbirds (Pelecaniformes, Ciconiiformes, Falconiformes, Charadriiformes) to the direct approach of a personal watercraft (PWC) and an outboard-powered boat to determine their flush distances. We used 11 sites with a mixture of low, moderate, and high amounts of human activity along the east and west coasts of Florida during September-November 1998 and April-June 1999. We detected considerable variation in flush distances among individuals within the same species and among species in response to both types of vessels. Average flush distances for the PWC ranged from 19.5 m ( Least Tern [ Sterna antillarum ]) to 49.5 m (Osprey [ Pandion haliaetus ]), whereas average flush distances for the outboard-powered boat ranged from 23.4 m (Forster's Tern [ S. forsteri ]) to 57.9 m (Osprey). Larger species generally exhibited greater average flush distances for both types of watercraft. A comparison of the flush distances elicited by each watercraft indicated that only the Great Blue Heron ( Ardea herodias ) exhibited significantly larger flush distances ( t test, p Ͻ 0.01) in response to the approach of the PWC than in response to the outboard, whereas four species (Anhinga [ Anhinga anhinga ], Little Blue Heron [ Egretta caerulea ], Willet [ Catoptrophorus semipalmatus ], and Osprey) exhibited significantly larger flush distances ( t test, p Ͻ 0.05) in response to the approach of the outboard-powered boat than in response to the PWC. Eleven species (68.8%) showed no significant difference ( t test, p Ͼ 0.05) in their flush distances in response to the fast-moving PWC and the outboard-powered boat. Our data suggest that a single buffer-zone distance can be developed for both PWC and outboard-powered vessels. Buffer zones of 180 m for wading birds, 140 m for terns and gulls, 100 m for plovers and sandpipers, and 150 m for ospreys would minimize their disturbance at foraging and loafing sites in Florida. Distancias de Amortiguamiento para Proteger a Aves Acuáticas en Actividades de Forraje y Descanso de la Perturbación por Embarcaciones Personales y Motores Fuera de BordaResumen: La recreación exterior y el ecoturismo pueden tener efectos negativos sobre la vida silvestre, por lo que es importante determinar áreas de amortiguamiento dentro de las cuales se limiten actividades cerca de áreas críticas para la vida silvestre. Expusimos a 23 especies de aves acuáticas ( Pelecaniformes, Ciconiiformes, Falconiformes, Charadriiformes) al acercamiento directo de embarcaciones personales (EP) y de una lancha con motor fuera de borda para determinar sus distancias de impacto. Utilizamos 11 sitios con una mezcla de actividad humana baja, moderada y alta a lo largo de las costas orientales de la Florida durante septiembre-noviembre 1998 y abril-junio 1999. detectamos una variación considerable en la distancia de impacto en...

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