Date: 4/30/26 10:40 am From: Ragupathy Kannan <0000013b0ad14faf-dmarc-request...> Subject: Latest on Red-cockaded Woodpecker research
From: American Ornithological Society <donotreply...>Date: Thu, Apr 30, 2026 at 12:22 PM
Subject: Bouncing back, but still losing chicks: The Puzzle of Partial Brood Loss
| Related paper: Increasing density from population recovery does not explain elevated partial brood loss in a threatened cooperative breeder by Lauren D. Pharr, Christopher E. Moorman, Nathan J. Hostetter, Clyde… |
|
| |
|
|
| | American Ornithological Society | Read on blog or Reader |
|
Bouncing back, but still losing chicks: The Puzzle of Partial Brood Loss
|
|
| |
|
By AOS on 30 April 2026
|
|
|
Related paper: Increasing density from population recovery does not explain elevated partial brood loss in a threatened cooperative breeder by Lauren D. Pharr, Christopher E. Moorman, Nathan J. Hostetter, Clyde E. Sorenson, Jeffrey R. Walters, Caren B. Cooper. Ornithological Applications.
|
|
When I started studying Dryobates borealis (Red-cockaded Woodpecker), I expected that one of the biggest challenges families faced would be competition at high population densities. After all, as conservation efforts helped these birds rebound across the Southeastern United States, many sites saw more groups packed into the same landscape than ever before. It seemed intuitive that higher density would strain resources and reduce nest success.
|
|
But the central finding of my dissertation surprised me: Even though populations have grown, partial brood loss—when some, but not all, chicks die—was not linked to population density at any of the three long-term study sites I examined, each monitored for over 40 years. In other words, I found little evidence for density dependence, which is the idea that as populations become more crowded, competition for resources increases, leading to a decrease in reproductive success or survival. Instead, brood loss appears driven by a combination of clutch size, timing, and group composition, with some evidence that late-stage brood loss is increasing over time. Understanding these patterns matters because they influence how we interpret “recovery” and how we plan for long-term sustainability of D. borealis populations.
|
|
|
Lauren stands in a longleaf pine forest, holding several newly hatched Red-cockaded Woodpecker nestlings in her palm. She smiles at the camera, her hands dusty from fieldwork. Photo courtesy of Lauren Pharr |
(left) An adult male Red-cockaded Woodpecker clings to the side of a pine tree, showing its distinctive black-and-white plumage and a small red patch on the side of its head. Resin flows down the bark around the cavity entrance. Photo by Brady Beck
(right) Three newly hatched Red-cockaded Woodpecker nestlings lie on a light-colored cloth, their bodies mostly featherless with developing pinfeathers visible. Two chicks wear tiny leg bands, and all appear to be only a few days old. Photo courtesy of Lauren Pharr |
|
Lauren smiles while holding a small group of Red-cockaded Woodpecker nestlings in her hand. She stands in a pine woodland with a pickup truck and field equipment, including a ladder, visible behind her. Photo courtesy of Lauren Pharr |
Lauren stands beside a pine tree marked with white paint bands, raising a long yellow cavity-inspection pole to check a Red-cockaded Woodpecker cavity. The surrounding forest consists of widely spaced longleaf pines and ground cover vegetation. Photo courtesy of Lauren Pharr |
|
|
Why I Asked this Question
|
|
D. borealis are one of North America’s most iconic cooperative breeding bird species. Groups consist of a breeding pair and, often, several “helpers”—usually older male offspring—who assist with everything from cavity maintenance to chick provisions. Cooperative breeding can buffer families against environmental stressors, so I wondered: Does cooperation also buffer them from density-dependent pressures as populations recover?
|
|
At the same time, managers across the Southeast have reported increased rates of partial brood loss. This pattern raised an important question: Are increasing densities unintentionally creating new reproductive challenges?
|
|
To answer this, I drew on the long-term monitoring data from the Sandhills of North Carolina, Marine Corps Base Camp Lejeune, and Eglin Air Force Base in Florida. These sites are among the most intensively studied D. borealis populations in the world, making them ideal for separating density effects from other ecological pressures.
|
|
What the Data Revealed
|
|
Across all sites, density—measured both as spacing among groups and the number of adults per hectare—had no detectable relationship with either early or late partial brood loss. This result held even as some populations reached or exceeded their historical group densities.
|
|
What did matter?
|
- Clutch Size: Larger clutches consistently experienced higher rates of partial brood loss, supporting the idea that D. borealis may produce more eggs than they can fully provision under suboptimal conditions.
- Group Composition: Groups with more adult males (breeding males and male helpers) had lower early brood loss across all sites, which is strong evidence that helpers play a meaningful role in supporting nest success.
- Lay Date: Later-season nests were more likely to lose chicks at some sites, particularly in the Sandhills.
- Time: At the Sandhills site, late partial brood loss has increased over the last four decades, pointing toward shifting environmental constraints, potentially linked to climate variability.
|
In short, demography, and phenology—not density—better explained brood loss patterns.
|
|
Why This Matters for Conservation
|
|
These findings suggest that current D.borealis recovery practices often create new cavity trees near existing groups, and are not inadvertently harming brood survival by increasing density. Cooperative breeding likely buffers many of the classic density-dependent pressures seen in non-cooperative species.
|
|
But the increase in late-stage brood loss at the Sandhills highlights an emerging concern: Climate-driven changes in resource availability or breeding phenology may change D. borealis productivity in ways density cannot explain.
|
|
As managers continue working toward long-term recovery, these results point to several priorities:
|
- Protecting and enhancing habitat features that support productive foraging, especially early in the season
- Monitoring shifts in breeding timing relative to climate
- Recognizing the critical role of helpers, particularly male helpers in supporting reproductive output
|
Ultimately, understanding the mechanisms behind brood loss helps ensure that recovery efforts strengthen not only population numbers, but also the capacity of families to successfully raise young.
|
|
A Final Reflection
|
|
Some of my favorite field memories are from quiet early mornings spent checking cavities, listening for the soft call notes of adults returning with food. Watching these families work together—breeders and helpers alike—made it clear why D. borealis has persisted despite decades of habitat loss. Their resilience is built on cooperation.
|
|
My hope is that by understanding how these families function, and where they remain vulnerable, we can help ensure their continued recovery in a rapidly changing world.
|
