Green Bay, Wisconsin is home to a variety of bird species, but one species in particular stands out as being rare and unique to the area. The rare bird found in Green Bay is the Kirtland’s Warbler.
What makes the Kirtland’s Warbler rare?
The Kirtland’s Warbler is considered an endangered species due to its extremely limited breeding habitat and small population numbers. Here are some key facts about why this bird is so rare:
- It nests almost exclusively in large stands of young jack pine trees. This specific habitat only exists for a limited time as the trees mature, requiring the warbler to continually find new jack pine stands.
- Historically, the Kirtland’s Warbler population dropped to only around 400 mating pairs in the 1970s. Conservation efforts have helped increase the population, but it remains relatively small with around 2,000 mating pairs today.
- The warbler breeds in the northern Lower Peninsula and Upper Peninsula of Michigan and winters in the Bahamas. Its limited migration route and breeding habitat range makes it vulnerable.
- Brown-headed cowbirds often lay eggs in the warbler’s nests, tricking the warblers into raising cowbird young instead of their own. This parasitic nesting relationship threatens the warbler’s reproductive success.
- Loss of jack pine habitat due to fire suppression efforts and development has reduced available nesting grounds for the Kirtland’s Warbler over the decades.
Due to these factors, the Kirtland’s Warbler has an extremely small worldwide population and depends on a very specialized habitat, making it one of the rarest warbler species in North America.
Where can Kirtland’s Warblers be found in Green Bay?
While Green Bay is outside the typical breeding range for Kirtland’s Warblers, they can sometimes be spotted during their spring and fall migrations when they pass through Wisconsin. Here are some of the top places bird enthusiasts should check to try spotting this rare warbler around Green Bay:
- Bay Beach Wildlife Sanctuary – This 700-acre urban wildlife refuge features migratory bird habitat and is along the shores of Green Bay. It offers excellent opportunities to potentially spot the Kirtland’s Warbler during migration.
- Barkhausen Waterfowl Preserve – Managed by the Wisconsin DNR, this wetland area provides stopover habitat for migratory songbirds. Birders may be able to catch sight of the warbler here.
- Point au Sable Natural Area – Located where the Bay of Green Bay meets Lake Michigan, this county park contains woodland, prairie, and shoreline habitat for migrating birds.
- Suamico River Area – The mixed forests and meadows along the Suamico River serve as habitat for spring and fall migrants, when Kirtland’s Warblers could pass through.
- Green Bay West Shores Wildlife Area – These excellent migratory woods and wetlands adjacent to Green Bay provide potential temporary habitat for the Kirtland’s Warbler during migration.
Since the Kirtland’s Warbler has such a small population, sightings in Green Bay are rare and not guaranteed. However, dedicated birdwatchers who regularly check prime migration habitats during spring or fall have the best chance of spotting this endemic rarity.
What does the Kirtland’s Warbler look like?
The Kirtland’s Warbler is a small, plump yellow and blue-gray songbird measuring about 5.5 to 6 inches in length. Here are some key physical features to help identify it:
- Bright golden yellow underside and belly
- Bluish-gray back and head
- Black streaking on the flanks
- White eye rings
- Dark gray legs and feet
- Long, pointed bill that is black on top and yellowish below
- Fanned tail with white outer tail feathers
- Male and females look similar
The warbler’s vibrant yellow belly and throat contrast nicely with its blue-gray hood and wings. When flitting through trees, its bold black streaks on the sides are also distinctive. The small size, fanned tail, and energetic movement of diving for insects can help identify it.
What is the Kirtland’s Warbler’s song and call like?
The voice of the Kirtland’s Warbler is loud and ringing, often described as overly loud for such a tiny bird. Here are details on its song patterns and calls:
- Song is a rapid series of repetitive phrases that end with a trill, such as “kit-KIT-kit-KIT-kit-wee-weet-weet-weet.”
- Sings insistently from high perches within its territory.
- Song has a far-carrying, loud, and emphatic quality described as “wooden” or “ventriloquial.”
- Call is a low, hoarse “chip” or “check.”
- Male’s song is the primary way mates attract and communicate with each other.
- Sings throughout the day during breeding season, especially early morning and evening.
Learning the Kirtland’s Warbler’s unique and loud song pattern is key for birders hoping to detect it during its brief migratory stopovers or on visits to breeding grounds. Stopping to listen carefully when in potential warbler habitat can help pick up the sounds of this rare species.
When and where does the Kirtland’s Warbler breed?
The Kirtland’s Warbler has an extremely limited breeding range and season compared to most warbler species:
- Nests exclusively in young jack pine forests, typically 5-20 years old, in Northern Lower Michigan and the Upper Peninsula.
- Depends on wildfires or human logging to create regenerating jack pine stands for nesting habitat.
- Breeding season runs from May through early August.
- Lays 3-5 eggs in cup-shaped nests low in jack pine trees, near the trunk.
- Both parents incubate the eggs for 13-16 days until hatching.
- Fledglings leave the nest at around 9-11 days old.
Successfully breeding Kirtland’s Warblers relies on the availability of large jack pine tracts that mimic the natural wildfire disturbance cycle that originally created its specialized habitat. Lack of habitat has caused major historical declines in this species.
What does the Kirtland’s Warbler eat?
The diet of the Kirtland’s Warbler consists largely of insects and other small invertebrates:
- Feeds on a wide variety of insects like beetles, ants, moths, caterpillars, grasshoppers, flies, and more.
- Will occasionally eat small fruits and berries.
- Forages for food in the lower branches and trunks of trees.
- Hawking behaviors includes flying out from perches to catch insects on the wing.
- Probes into pine needles and dead leaves searching for insect prey.
- Parents feed nestlings a diet of insects and spiders.
- Winter diet consists of insects like beetles, butterflies, ants, wasps, and moths.
The warbler’s foraging techniques and prey preferences are well-adapted to pick insects off jack pines and out of the air. Its varied insect diet provides plentiful nutrition for the high energy demands of migration and breeding.
What is the conservation status of the Kirtland’s Warbler?
The Kirtland’s Warbler is federally listed as an endangered species and considered one of the rarest warblers in the United States. Here is a summary of its conservation status:
- Listed as endangered under the Endangered Species Act since 1967.
- Populations declined to only 167 breeding pairs in 1974, but have rebounded to over 2,000 pairs today thanks to conservation efforts.
- Habitat management, cowbird control, captive rearing, and public education programs have aided the species.
- Restricted exclusively to Michigan for breeding habitat.
- Total global population estimated at over 5,000 individuals.
- Threats include loss of jack pine habitat, brood parasitism, and high nest predation.
Ongoing habitat conservation and expansion of jack pine forests will be critical for the Kirtland’s Warbler’s future. While still endangered, protections and breeding programs have made a significant difference helping populations rebound from near extinction.
Fun Facts about the Kirtland’s Warbler
Here are some interesting and unique facts about this rare yellow and blue songbird:
- Named after Dr. Jared Kirtland, 19th century Ohio naturalist and physician who first collected the species.
- One of the first birds identified as endangered in the United States.
- Depends on wildfire or logging to create the open jack pine stands where it nests.
- The loud, ringing song of the male can carry up to a half mile away.
- Male Kirtland’s return to their same territory and mate each breeding season if they survive migration.
- Their oversized song is thought to be an adaptation to singing over the noisydin of early northern spring when they establish territories.
- Nestlings develop quickly, ready to leave the nest after just 9-11 days.
- At around 3 weeks old, young warblers can feed and fend for themselves.
The unique lifestyle of this rare warbler species makes it a fascinating case study in the adaptations of endangered birds. Hopefully ongoing conservation efforts ensure the Kirtland’s Warbler continues to grace the jack pine forests of the Midwest with its outsized song for years to come.
Where else can the Kirtland’s Warbler be found?
While the Kirtland’s Warbler breeds exclusively in a limited range in Michigan, it can be found in other locations during migration and in its wintering grounds:
- Migrates through Wisconsin, Ontario, Ohio, Indiana, Illinois, and points farther south in Fall and Spring.
- Winters almost entirely in the Bahamas from late November through early May.
- In the Bahamas, frequents scrub habitat and areas with low vegetation.
- Rarely appears outside breeding range and migration route.
- On very rare occasions, may show up on the Atlantic coast during migration.
- Accidental sightings have occurred in Florida, Nova Scotia, and Bermuda.
Since the Kirtland’s Warbler has such strict habitat preferences and a limited range, it can only be reliably found in migration hotspots and wintering grounds in the Bahamas outside the breeding season. But vagrant individuals sometimes appear well outside their expected locations on occasion, creating exciting opportunities for birders.
How can I attract Kirtland’s Warblers to my backyard?
Unfortunately, attracting Kirtland’s Warblers to a backyard just outside their normal range and habitat is extremely unlikely. Here are some reasons why:
- Does not occur regularly outside a limited migration route and small wintering range.
- Relies on specific young jack pine forest habitat for breeding.
- Rarely visits bird feeders or backyard habitats.
- Extremely specialized diet makes it difficult to entice with food.
- Fairly shy and easy to disturb.
Backyards would need ideal jack pine forests with the right territorial space, isolation, and insect populations to potentially attract nesting Kirtland’s Warblers. Since their geography is so limited, an accidental sighting during migration would be the best backyard birders could hope for. The best way to see this rare species is visiting its habitat in Michigan or the Bahamas!
Conclusion
In summary, the Kirtland’s Warbler stands out as one of the rarest and most unique bird species that can occasionally be spotted in Wisconsin. This small yellow and blue songster depends on a highly specialized jack pine forest habitat for breeding and faces ongoing conservation threats. While endangered, its numbers have rebounded thanks to dedicated habitat management and cowbird control programs. Birders hoping to catch a glimpse of this rare beauty should watch for it during migration through Wisconsin hotspots or plan a dedicated birding trip to its Michigan breeding grounds. With committed ongoing conservation efforts, hopefully future generations will still be able to enjoy encounters with the special Kirtland’s Warbler.
References
- https://www.audubon.org/field-guide/bird/kirtlands-warbler
- https://www.fws.gov/midwest/endangered/birds/Kirtland/kiwafctsht.html
- https://www.michigan.gov/dnr/0,4570,7-350-79136_79608_85968_95974—,00.html
- https://journeynorth.org/Kirtland/KirtlandFacts.html
- https://www.savingcranes.org/kirtlands-warbler-range-map-breeding-grounds-migration-route-wintering-grounds/
