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Status of the Golden-winged Warbler in North Georgia, and a Nesting Record of the Lawrence's Warbler
STATUS OF THE GOLDEN-WINGED WARBLER IN NORTH GEORGIA, AND A NESTING RECORD OF THE LAWRENCES WARBLER
Nathan A. Klaus
Golden-winged Warblers (Vermivora chrysoptera) were considered fairly common summer residents in North Georgia when Burleigh wrote Georgia Birds in the 1950s. There are numerous records for Golden-winged Warblers during this time, and they were found in at least five counties: Fannin, Dawson, Union, Towns, Dade, and possibly, a sixth, Whitfield (Burleigh 1958). There is also substantial evidence that Golden-winged Warblers were common in the Southern Appalachians, including North Georgia, during the 1800s if not earlier. One of the earliest ornithological explorations of the Southern Appalachians (Brewster 1886) found Golden-winged Warblers to be quite common, especially in open oak savannah and second growth on hillsides (implying then that they were found in both logged and unlogged areas). It is interesting to note that nothing resembling open oak savannah remains in the Southern Appalachians, probably due to fire suppression and historic logging. This may explain the apparent dependence of Golden-winged Warblers upon artificial habitats such as clearcuts that are found today (Klaus 2001). In addition to William Brewsters and Burleighs well-documented records, a nest was found in Georgia in 1859 by Alexander Gerhardt (Burleigh 1958).
In recent decades populations appear to have declined dramatically. Nowhere in the Southern Appalachians can Golden-winged Warblers be considered common, probably due to changes in habitat availability. Besides the elimination of open oak savannahs frequented by Golden-winged Warblers in Brewsters time, changes in land use have further reduced available habitat. Clearcutting, which provides valuable habitat for this species (Klaus 2001), is a management tool rarely used today by the major landowner in the area, the U.S. Forest Service (USFS). The USFS owns nearly half of some counties within the historic Georgia range of Golden-winged Warblers (i.e. Union County, 45% USFS). Furthermore lands at suitable elevation for Golden-winged Warblers (generally greater than 2,800 ft) throughout the Southern Appalachians are nearly all owned and managed by the USFS. The reduction of early succession habitat on USFS lands is a likely a major cause of the decline of this species of warbler. Private land in North Georgia, which once consisted of subsistence farms and which provided habitat in the form of old fields and woodlots, is today, composed of primary and secondary homes, usually with either mature forest or residential lawns. Combined, these changes in land use on public and private land are probably responsible for the widespread elimination of Golden-winged Warblers from North Georgia. This includes numerous areas noted by Burleigh and others for their Golden-winged Warbler populations, which are no longer occupied, including: Blood Mountain, Young Harris, Lake Winfield Scott, and Ivy Log. Very little new habitat has been created in the last decade, leading to serious concerns for this species viability in North Georgia and throughout the Southern Appalachians.
Six sites were found occupied (Figure 1), five within 10 miles of one another. Three of the five sites were on private land in old field habitat (the Johnny Gap sites); one was in an area damaged by hurricane Opal and later salvage-logged (Brawley Mtn.), and one was at the site of an intense fire (Chestnut Mtn.). Sixteen Golden-winged Warblers (not including hybrids) were seen over four years (Table 1). Very little early succession habitat was encountered at locations of suitable elevations.
Though no nests were found, evidence of reproduction was observed at two sites. On May 7, 1999 at the Johnny Gap 1 site, the female of the pair was seen carrying nesting material. A thorough search revealed no nest and it was assumed that nest building was in its earliest stages. Unfortunately, the site was not revisited later that season and was taken over by Blue-winged Warblers (Vermivora pinus) the following year. On June 4, 2002 at the Brawley Mtn. site, two indications of reproduction were witnessed. The first involved a female Lawrences Warbler, which responded to the Type II Golden-winged Warbler playback. She approached within 20 feet carrying what appeared to be a Lepidopteron larvae and flew off within a few minutes. She was later seen two other times making trips (assumed to be carrying food) in a similar heading, but no nest or young were located. To our knowledge this is the first record of a Vermivora chrysoptera x Vermivora pinus hybrid nesting in Georgia, though this is not unexpected, since most Golden-winged Warbler populations in Georgia are sympatric with Blue-winged Warblers.
Approximately two hours after the sighting of the female Lawrences Warbler, a male Golden-winged Warbler was seen carrying food. Upon following his line of flight over several trips, five recently fledged (still downy) Golden-winged Warblers were discovered being fed by the male and foraging in a recently logged area. Though the young were observed over the next two hours, no female was seen in their vicinity. It is assumed that the female Lawrences Warbler was not their parent since she was seen in a different location, and carried her food in a different direction. In addition, all five young appeared to be phenotypically pure.
The first priority in managing this species should be to augment remaining populations, although it is unlikely that Georgias population(s) is viable on its own. It is estimated that 1,000 breeding pairs are necessary for a species dependent upon ephemeral habitat to have a viable population; viability in this case being defined as having a 95% probability of being extant in 100 years (Thomas 1990). Luckily wildlife populations do not recognize political boundaries. North Carolina still maintains a sizeable population of Golden-winged Warblers, especially on the Cheoah and Wayah ranger districts of the Nantahala National Forest. By maintaining connectivity (grouped patches of early succession habitat along high elevations) to the North Carolina Golden-winged Warbler population it is likely that North Georgia populations can continue at least as a meta-population. Besides augmenting existing populations, maintaining this connectivity through the strategic creation of habitat at appropriate elevations should be a management priority. Relatively small patches of apparently suitable habitat, which go unoccupied, are probably the result of lack of viability. Lacking a source population to fill this habitat, these potential sites go unoccupied.
Loss of suitable habitat is extirpating Georgias Golden-winged Warbler populations and threatens to eliminate them from the southeast. Creating new habitat through a combination of prescribed fire or timber harvests is the only way to keep this species in the Southern Appalachians. Although some may advocate prescribed fire alone to create Golden-winged Warbler habitat, only one site in the Southern Appalachians known to have Golden-winged Warblers was created through fire, Chestnut Mountain. This site was only found occupied in 2002. Using fire of this intensity may not be practical in many areas to create habitat, but it is interesting to note that natural forces, such as fire, are capable of creating habitat for this species of warbler. Unfortunately, these natural forces have been suppressed for nearly a century, even in designated wilderness areas. It is implausible to rely on natural forces to provide early succession habitat while actively suppressing wildfire. Using timber harvests to establish early succession habitat, followed by repeated fires of manageable intensity to maintain it may be a more practical approach. Although the use of fire to maintain high elevation early succession habitat was until recently theoretical, Golden-winged Warblers seemed to respond well to prescribed fire in 2003 on Brawley Mountain.
Georgias Golden-winged Warbler populations have dramatically declined in recent decades. Populations in adjacent Tennessee and North Carolina face similar threats and are experiencing dramatic declines. Without coordinated active management on the part of the USFS and state wildlife agencies, the long-term viability of the Southern Appalachian population of Golden-winged Warblers is in question. Georgia once supported a sizeable population of Golden-winged Warblers and can again make a significant contribution to the conservation of this species.
Figure 1. Area surveyed and site found occupied by Golden-winged Warblers, 1999-2003. Areas in black are USFS, white lines are major roads, and black lines are county lines. Areas found occupied by Golden-winged Warblers are indicated with a cross.
Table 1. Locations of all Golden-winged Warbler and hybrid sites found through survey efforts, 1999-2003.
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