Recovering the Golden-winged Warbler
A Look at Declining Populations, Habitat and a Chance for Recovery
Over the past 60 years , a tiny songbird has lost nearly 66% of its breeding population, making it the smallest population of any songbird not on the Endangered Species List. This is the current situation of the Golden-winged Warbler (Vermivora chyrsoptera).
This reduction in breeding population (down to approximately 400,000 individuals) has occurred in both of its regional populations – The Great Lakes and Appalachian Mountains – but the largest decline at 98% has been observed in the Appalachian Region.
Basic Biology
Appearance
Breeding males are mostly silver or gray with gold markings on the wing below the shoulder and atop the head. Males also have a black mask and throat, two white face marks, and a light chest.
Appearance
Breeding females have very similar markings as the breeding males, although their colors are a bit more dull, with the gold marks having a slight green tint and the throat patch resembling a dark gray rather than black. Females do not display a face mask. They also have a sharply pointed thin bill.
Songs and Calls
Males sing a buzzy, two part song: a long note on a high pitch followed by 3-6 shorter, lower notes.
Songs and Calls
Another song, often given repeatedly before dawn, is a rapid stutter followed by lower buzzy notes. It is associated with territorial defense.
Range
The golden-winged warbler migrates between summer breeding grounds in eastern and north central areas of the United States – The Great Lakes Region (including southern Canada) and the Appalachian Mountain Region – and winter grounds in Central and northern South America. The long distance migration takes place down through the eastern and mid-western regions of the US, between the Mississippi River and the Appalachians. This migration south typically takes place in late August into September. To return to their breeding grounds, migration to the north will begin in the in April. The animation from Cornell Lab of Ornithology's abundance animation below represents this migration below by week.
Source (used here for educational purposes only).
Population in Decline
From the prior animation, the viewer can see that part of the migration route of the warbler takes place through the Midwest region. That geographical area between the current two sub populations was once part of the breeding Range (during the 1970’s). Facing the sharpest decline of any songbird, there are three main reasons for suspected decline.
(#1) Breeding Habitat Loss: Nature has always done its due diligence in creating ideal golden-winged warbler habitat, from natural storm events, forest fires and beaver dams emerged the early successional habitat patches needed for nesting, adjacent to mature forests for fledgling and adult survival. Due to large-scale timber harvesting over several years (and regrowth of the those harvests), expansion of human activity, fire suppression, and a lack of abandoned farm ground, major habitat loss has occurred, leaving less breeding grounds available.
Image Source - used here for education purposes only.
(#2) Winter Habitat Loss: The wooded areas needed for overwintering habitat in Central America has also shown a decline as forests are cleared for agricultural production (palm oil and sun grown coffee).
(#3) Hybridization with Blue-winged Warbler: The blue-winged warbler is very closely related to the golden-winged warbler and the two species have been known to interbreed over time. Resulting offspring are known as the Brewster’s and Lawrence’s warblers. While these hybrids occur naturally and are fertile – the continued hybridization lead to less pure golden-wings, further decreasing the population. Shifting ranges is at play in leading to increase interaction between the two species, with golden-wings preferring the ridge tops/higher elevations, and blue-wings in the valley areas. Shifts in climate have lead to blue-wings moving to higher elevations.
Male 'Lawrence's Warbler', Frontenac, ON, 23 June. The F1 'Brewster's Warbler' show the dominant traits of the pair; the F2 hybrid 'Lawrence's Warbler' shows the recessive traits, namely yellow underparts and bold head pattern. Jun 24, 2009; photographer Frode Jacobsen (used here for educational purposes only)
Male Golden-winged Warbler (right) with hybrid 'Brewster's Warbler', Opinicon Lake, ON, 20 June. Hybrids between Golden-winged and Blue-winged Warbler are common. Most F1 hybrids have white underparts like Golden-winged, but a reduced head pattern with a dark eyeline like Blue-winged Warbler. Jun 21, 2009; photographer Frode Jacobsen (used here for educational purposes only)
Map displays overlapping range of the golden-winged and blue-winged warblers (as of 2011-2012). Source (used here for educational purposes only)
Early Successional Habitat Dwellers
Recovery and Conservation Efforts
Specifically - let's focus in on the Appalachian Mountains sub-population, as it has lost approximately 95% of it's breeding numbers.
In November of 2011, a collaboration of those that make up the Appalachian Join Venture, US Fish and Wildlife Services, and the American Bird Conservancy occurred to develop a guide, "Golden-winged Warbler Habitat: Best Management Practices for Forestlands in Maryland and Pennsylvania". Which provides a wonderful descriptive habitat development layout for landowners and forest managers to utilize in creating the most effective habitat - particularly in Maryland and Pennsylvania. All information within the section is from the guide.
As is evident - early successional habitat does not stay in its early successional stage. After approximately 10-15 years (depending on location), stands that were cut to create early successional habitat will be "overgrown" in a sense, no longer providing the most ideal nesting habitat. Short interval management is an important factor in continuation of habitat for the golden-winged warbler. This guide also outlines the features that will allow for maximizing the best outcome of habitat. I'll outline a few, but the guide provides much greater detail.
Landscape Scale
Golden-winged warblers need that early successional habitat with surrounding mature forests - approximately 70% of the landscape within 0.5 miles of the harvest site should be forested. Elevations of 950' and higher are recommended to minimize interactions between golden-winged and blue-winged warblers. Areas where populations of blue-winged exists - higher elevations are preferred. Landowners should take advantage of other previously disturbed sites, planned future harvest in where habitat will be created. Habitat should be created within 1 mile of existing habitat, as golden-winged warblers tend to return to the same sites each year.
Three early successional stands within the forested landscape (photo by John Long). Used here for education purposes only.
Temporal Scale
Providing young forest/early successional habitat over a large project area might be most ideal for that warbler and will require some in depth and long term planning. As stated before, warblers may not utilize stands older than 15 years old to nest, but need (post-harvest) vegetation approaching the 4 year mark up to 15 years (or 20). Before harvest, successful regeneration of desirable hardwoods species should be present - including lack of interference from invasive species, and protection from deer browse pressure. Site prep of these sites can take several years, showing an even greater need for active management. Creating several different age patches within a large area over time might be the best approach.
Stand Scale
As nest building typically takes place along the edge between shrubby open habitat and the forest (within 250 feet), project boundary shape is important. The longer and more irregular the shape of the area is, the more forest edge is created, leading to an increase in possible nesting sites. Feathering (or thinning) of the forest edge also provides a bit more diversity for the site and can be beneficial for other species that will utilize the area.
Left image displays irregular shape for an increase in forested edge; Right image shows a feathered edge. (Photo by Andrew Vitz). Used here for educational purposes only.
Overall, creation of this early successional habitat is beneficial, not only to a small bird that has a rapidly declining population, but for other species that may dwell in similar types of habitat. I do believe that creating wildlife habitat can also be tied into better forest stand management overall. Landowners can couple efforts to boost habitat with maintaining healthy stands of for timber projection and recreational use. Financial and technical assistance can be found assistance within the sub-population areas through contacting state departments of natural resources, as well as federal agencies, such as the USDA - Natural Resources Conservation Service.
Additional Habitat Guides
https://www.birds.cornell.edu/home/wp-content/uploads/2019/05/GWWA-GLRegionalGuide_130808_lo-res.pdf (Great Lakes Region Habitat Guide)
https://www.birds.cornell.edu/home/wp-content/uploads/2019/05/GWWA-APPLRegionalGuide_130808_lo-res.pdf (Appalachian Region Habitat Guide)
