Tricolored Herons are widespread along the Texas coast where they nest with other colonial waterbirds in small to large colonies. Except for the non-native Cattle Egret (Bubulcus ibis), Tricolored Herons are the most numerous of the heron species in Texas. This species was not commercially important to the plume trade; thus, this heron was not directly decimated during the era of plume hunting. However, since these birds nest in association with plume-bearing species, disturbance to heronries must have had some adverse effect upon them locally until they received legal protection and the benefit of conservation and management efforts.
In Texas, an important influence on waterbird populations is the 20-25 year precipitation cycle (Telfair 2002). Between the early 1960s and late 1980s, there was a significant upward trend, more recently the trend has begun to reverse (Tom Spencer, Texas Forest Service, pers comm.). The trend varies regionally and there are intermittent drought yearsand irregular intervals with pronounced wet/dry springs-summers such as those associated with El Niño/La Niña years and massive slow-moving atmospheric disturbances. Inland wetland habitats are particularly subject to the effects of these trends. Unfortunately, there is a lack of data about the status of the Tricolored Heron in Texas before the 1970s; so, the possible relationship between its breeding populations and the precipitation cycle is unknown for earlier years.
The dark color of Tricolored Herons in inconspicuous small and even large nesting colonies makes the species difficult to census accurately except by ground-based surveys.
DISTRIBUTION: The Tricolored Heron is abundant; but, is mostly coastal in estuaries, lagoons, swamps, and marshes within the Coastal Prairies region. Specific habitats include mud flats, salt and fresh water marshes, tidal creeks, shrub swamps, open shallow bays, and human-made habitats, especially, flooded rice fields and aquaculture ponds (Kushlan and Hancock 2005).
According to the records of Oberholser (1974), the Tricolored Heron is a coastal resident, breeding locally with irregular occurrences in summer in central and north Texas with no confirmed nesting records north of Colorado and Austin counties. An inland report of breeding far to the northeast at Caddo Lake in Marion County was questionable. However, beginning in the early 1970s, and continuing to the present time, there are breeding records that indicate inland expansion: in southeast Texas, in 1973, two pairs nested at McCardell’s Lake, Polk County and, in 1975, three pairs nested at Steinhagen Reservoir, Jasper County (Mullins et al. 1982); and, in 1979. In north central Texas, three pairs nested at Cedar Creek Islands Wildlife Management Area in Cedar Creek Reservoir, Henderson County (Runnels 1980); in 1990, a pair probably nested at the Southside Water Treatment Plant in southeast Dallas County (Peterson 1991). In 2003, 2005, and 2006, 2 pairs nested at the Southwestern Medical Center in Dallas County(Clark Scott, in litt.); and, in 2004, three nests were reported in Dallas County, but no location was given (Lockwood 2004); and, in 2005, three nests were found at the eastern edge of the Edwards Plateau in west San Antonio, Bexar County (Lockwood et al. 2005). Since 1979 (1980-2004), breeding has occurred annually at Cedar Creek Islands Wildlife Management Area, but the population has remained small (5-38 pairs). Based upon Texas colonial waterbird censuses (1973-1990), most of the breeding population is coastal (94-99.9%).
SEASONAL OCCURRENCE: Breeding extends from late March to late August; eggs, April 5-June 23; nestlings early May to August 28 (Oberholser 1974, Telfair 1983). In late summer and fall, these herons are uncommon to rare visitors in the eastern third of the state and have been recorded twice in the southeast Panhandle during September (Donley and Gray counties). There are postbreeding wanderers in the South Plains and in recent years, almost annually in the Concho Valley of the Edwards Plateau and westward through the Trans-Pecos during all seasons except winter. There are several winter records from northeast Texas (Lockwood and Freeman 2004).
BREEDING HABITAT: Tricolored Herons nest primarily in herbaceous plants, shrubs, and small trees on coastal islands and within coastal marshes, swamps, lagoons, and streams. They are colonial nesters, in small single-species colonies or in large multi-species colonies. However, they are less social than other species; so when nesting with other species, they usually nest in peripheral areas in low dense, well-shaded shrubs and small trees in which their nests are placed less than 3 m (10 ft) above the water or ground. Occasionally they may nest on the ground (Frederick 1997, Kushlan and Hancock 2005).
STATUS: According to Texas colonial waterbird censuses from 1973-2000, the breeding population of the Tricolored Heron fluctuated between 6,113 and 16,860 pairs (McFarlane 2002). Telfair (1993) analyzed the trend data between 1972-1990 and foundthe breeding population had anannual decreasing trend of-1.9%. McFarlane (2002) extended the trend analysis from 1973-2000 and found a highly significant annual decreasing trend of -3.0%). Between 1973-1990, and especially between 1982-1990, there was a gradual decrease in the number of large colonies of Tricolored Herons (Telfair 1993). Nevertheless, within these time spans, there were years with high census numbers; so, the decline may be related to regional responses to theprecipitation cycle (see Introductory discussion above). North American Breeding Bird Survey data for Texas (Sauer et al. 2005) give annual trends of 9.1% (1966-1979), -5.2% (1980-2005), and -1.3% (1966-2005); thus, supporting the decreasing trend indicated by colonial waterbird census data.
Text by Raymond C. Telfair II (2007)
Frederick, P. C. 1997. Tricolored Heron (Egretta tricolor). In The Birds of North America, No. 306 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PAKushlan, J. A. and J. A. Hancock. 2005. The herons. Oxford Univ. Press Inc., New
Lockwood, M. W. 2004. Texas (nesting season). N. Am. Birds 57: 513-518.
Lockwood, M. W. and B. Freeman. 2004. The TOS handbook of Texas birds. Texas A&M. University Press, College Station.
Lockwood, M. W., R. Pinkston, and R. Weeks. 2005. Texas (nesting season). N. Am. Birds 59: 620-625.
McFarlane, R. W. 2002. Texas colonial waterbird trends (Powerpoint presentation). http://www.fws.gov/texascoastalprogram/TCWC.htm.
Mullins, L. M., G. W. Blacklock, D. R. Blankinship, A. H. Chaney, S. Kennedy, K. A. King, R. T. Paul, R. D. Slack, J. C. Smith, and R. C. Telfair II. 1982w. An atlas and census of Texas colonial waterbird colonies 1973-1980. Texas Colonial Waterbird Soc., Caesar Kleberg Wildl. Res. Inst.., Texas A&I University, Kingsville.
Oberholser, H. C. 1974. The bird life of Texas. University of Texas Press, Austin.
Peterson, J. J. 1991. City of Dallas water treatment plant produces three unusual north central Texas nest records Bull. Texas Ornithol. Soc. 24: 25-27.
Runnels, S. R. 1980. Louisiana Heron (Hydranassa tricolor) breeding in north central Texas. Bull. Texas Ornithol. Soc. 13:23-24.
Sauer, J. R., J. E. Hines, and J. Fallon. 2005. The North American Breeding Bird Survey, results/analysis 1966-2005. Version 6.2.2006. USGS Patuxent Wildl. Res. Cnt., Laurel, Maryland. http://www.mbr-pwr.usgs.gov/bbs/bbs.html.
Telfair, R. C. II. 1983. The Cattle Egret: a Texas focus and world view. Kleberg Stud. Nat. Resour. Tex. Agric. Exp. Stn., Texas A&M Univ., College Station.
Telfair, R. C. II. 1993. Cattle Egret (Bubulcus ibis) population trends and dynamics in Texas (1954-1990). Nongame and Urban Program, Fish. and Wildl. Div., Texas Parks and Wildl. Dept. PWD-RP-N-7100-234, Austin.
Telfair, R. C. II. 2002. Inland heronries in Texas. Texas Partners in Flight Newsletter, Texas Parks and Wildl. Dept. 9: 20.