This summer I was lucky enough to work as a Kirtland’s warbler nest monitor in Wisconsin. Now for those of you who don’t know – Kirtland’s warblers are an endangered bird species that relies on a very specific type of habitat. Read on to find out more about the Kirtland’s warbler in Wisconsin and what conservation of an endangered species can be like!
What is a Kirtland’s Warbler?
The Kirtland’s warbler is a bird – which immediately makes it AWESOME! But not only is it a bird, it is a rare, endangered bird in the Wood Warbler family (Wood Warblers are found only in the Americas).
Male Kirtland’s Warbler.
Photo: Ashley Hannah 2014
Why is it rare?
Kirtland’s warblers are rare because of their strict habitat requirements – they only breed in young stands of jack pine or mixed red pine-jack pine stands. Jack pine is a species of pine tree that relies on fire to release seeds from the cones. Fire also helps prepare the soil for seed germination. Historically wild fire also maintained a patchwork landscape of jack pine forests at the right age and created openings within stands suitable for Kirtland’s warblers to nest in. When Europeans settled the continent though wildfire suppression began.
The 2010 Meridian Fire burned thousands of acres of Huron-Manistee National Forest and Michigan DNR lands.
Photo: US Forest Service 2010.
Without wildfires Kirtland’s warbler habitat would slowly disappear unless it was created some other way. So, management agencies and researchers (particularly in Michigan) have come up with ways to create young jack pine stands suitable for Kirtland’s warblers. Some of these include: logging, burning, seeding, and replanting on a rotational basis. You can read more about management here.
Also with the advent of European settlement Brown-headed cowbirds expanded their range into the range of Kirtland’s warblers. Brown-headed cowbirds have a unique life strategy: they lay their eggs in the nests of other bird species and allow the hosts to raise cowbird young. Also, cowbird exhibit mafia and farming behavior (read about it here). Birds such as Kirtland’s warblers never evolved with this parasitism pressure and have not adapted any methods to deal with this.
Brown-headed cowbird.
Photo: Rodney Campbell 2013
To reduce the rate of parasitism of Kirtland’s nests by cowbirds management agencies trap cowbirds to remove them from the breeding sites.
A Quick History of Kirtland’s Warblers in Wisconsin:
Individual Kirtland’s warblers had been recorded in Wisconsin for many years, but were never recorded nesting in the state until 2007, when a bird watcher found three territorial males, a female, and a nest with five eggs on a commercial red pine plantation! In 2008 nest monitoring began and has continued through present.
Kirtland’s Warber Nest.
Photo: Ashley Hannah 2014
Also, every year any males that do not have bands on their legs are captured and banded. This helps to identify individual males, define the territories of each male, and determine which nest belongs to which male. It also helps to figure out if they are returning and how long they live. Males exhibit site fidelity and will often return to the same territory each year. One of the oldest returning males is 8 years old!
This male was given the moniker AOGG because he has an aluminum US Fish and Wildlife Service band and an orange band on his left leg, and two green bands on his right leg. Each male has a unique combination of one aluminum band (each of these has a unique number) and three colors.
Photo: Ashley Hannah 2014
So what does nest monitoring entail?
Nest monitoring entailed earlier mornings, wet feet, and lots of walking through red pine rows. The males sing most actively in the morning so nest monitors have to get out their bright and early (which means lots of wet grass!). I began in mid-May identifying the males who had just returned from their wintering grounds. Identifying the males is a fine art – you first have to first locate a male (usually not to difficult because they are very vocal and loud), then follow the song to the bird, and then either get close enough to see the band color combinations on the legs or take a photo with a camera and zoom in on the band combos that way. Once the males are identified then you get to follow them around taking GPS coordinates at the trees they frequently sing in. With those coordinates, you can figure out the territory boundaries of each male.
Singing Male Kirtland’s Warbler.
Photo: Ashley Hannah 2014
About the first week of June is when the second nest monitor came in and then each monitor begins to look for signs of nesting. This is a bit more tricky than defining territories. Females are very hard to spot because they skulk around low in the trees and don’t make much noise at all. So, we got to follow the males around looking for them to show behaviors that indicated they had a nest. The most easy to observe behavior was when a male would sing with food in his mouth (don’t ask me how, but they can do it!). However, that then meant you had to observe the male and try to figure out where he went to feed the female. Males bring the female food – once she lays eggs she rarely leaves the nest. But the nests are hidden in clumps of grass or under low pine branches, and if you get close to a nest the male might just eat the food instead of revealing the location of his nest.
Kirtland’s Warbler Nest.
Photo: Ashley Hannah 2014
The above photo is a close up of a nest. Now just look at the photo below and try to find the nest (click on it to see a large image). Now you can see how it might be hard to find a nest.
Kirtland’s Warbler Nest.
Photo: Ashley Hannah 2014
Once we located nests we then got to watch them (from a distance). Based on the behaviors of the adults we could tell if the nests had hatched or not. Prior to hatching the female would hardly leave the nest and the male would bring her food; once chicks hatched she and the male would be frantically bringing food back to feed the growing babies. We watched the nests until the chicks fledged (which usually happened between 10 and 13 days after they hatched) or when the nest was abandoned (because of predation usually). Once the chicks left the nest we checked on the family groups until July when all the nests had fledged.
One of the most rewarding experiences of this job was seeing the chicks fledge and knowing that my work was helping to add to the knowledge of these birds.
If you want to read more about the population of Kirtland’s warblers in Wisconsin please visit the US Fish and Wildlife Service Wisconsin Kirtland’s Warbler Updates page, the Wisconsin DNR Kirtland’s page, and the Wisconsin Kirtland’s Warbler Project Facebook page.
If you want to help fund Kirtland’s Warbler conservation and management in Wisconsin, and you live in Wisconsin think about participating in the Great Wisconsin Birdathon. Find out more information here.
Thank you for reading! If you have questions, comments, or stories about Kirtland’s I would love to hear them – just tweet at me or leave a comment below!
Peep-Lo 
June 19, 2023 at 5:59 am
good day, fine blog on oleaginous loss. the like helped.