The Perfect Storm For A Challenging RCW Season

In Spring 2024, The Jones Center at Ichauway entered its 26th Red-cockaded Woodpecker (RCW) monitoring season. As a Safe Harbor program member since 1999, Ichauway has devoted vast resources to restoring the RCW population to its 29,000 acres.

Despite a relatively strong population uptick following Hurricane Michael’s substantial impacts in 2018 (nearly 20% of Ichauway’s cavity trees were lost overnight due to the storm), the Center’s Forestry & Wildlife Biologist, Zach Henshaw, had mixed feelings on 2024’s outlook leading into April. Nuances during the 2022 and 2023 nesting seasons were at play.

An Ichauway RCW cavity tree marked with painted, white rectangles.
An Ichauway RCW cavity tree marked with painted, white rectangles.

“We were hoping this year would be the upturn season. Two years ago, was an awesome RCW season, while last year [2023] trended down. We suspected this year was going to be either boom or bust,” said Henshaw.

In 2022, the population produced an impressive 41 successful nests, 83 banded nestlings, and ultimately 59 fledglings from 46 potential breeding groups (PBGs), which are the most reliable unit of measurement to gauge a population’s status.

Comparatively, in 2023, the population increased to 52 PBGs; however, it produced less successful nests (38), less banded nestlings (76), but more fledglings (68).

Three RCW hatchlings inside a cavity.
Three RCW hatchlings inside a cavity.

The Banding Blitz

This season’s first eggs were laid on April 11 and the countdown began. The banding period is a mad dash for Henshaw for a few reasons.

RCWs are known as asynchronous nesters, meaning eggs may not hatch simultaneously. Eggs are laid during a multi-day period, typically one per day, until the clutch is complete (typically 2 – 4 eggs) and undergo a mere 10-day incubation period. Banding must occur during a “sweet spot” in nestling size from 5-11 days old. Before 5 days, the nestlings’ legs aren’t large enough to accommodate multiple bands. Wait after 11 days and their eyes are open, and feathers are emerging, making capture more difficult and likely to cause injury. This means nest checks are needed at regularly timed intervals to accurately age new hatchlings to ultimately band birds safely.

Banding, especially for endangered species, requires federal and state permits and an experienced bird bander. These regulations are in accordance with the Migratory Bird Treaty Act and the Endangered Species Act.

In addition to a uniquely numbered USGS aluminum band, chicks receive a combination of plastic, colored bands on both legs.
In addition to a uniquely numbered USGS aluminum band, chicks receive a combination of plastic, colored bands on both legs.

Early Red Flags

It wasn’t far into the monitoring season before Henshaw realized things weren’t shaping up to be that banner year for which he had hoped.

Despite the number of PBGs increasing from 37 in 2017 to 57 in 2024, the number of fledglings produced this year (38) was only slightly higher than in 2017 (34). What was the cause? In a nutshell, a combination of factors could have been at play creating a perfect storm – most notably, consecutive years of female-skewed fledglings, an especially rainy spring with unfortunately timed downpours, and intense cavity competition. More on that later.

Back to the Beginning

First, let’s take a step back and delve into a brief history of the RCW population at Ichauway.

In 1999, there was a single, male RCW remaining on Ichauway. To accelerate population recovery, The Jones Center received translocated birds annually for most years between 1999-2015. Many of the birds were received from the Apalachicola National Forest. Other donor locations included Fort Stewart Army Base, Fort Moore Army Base, Eglin Air Force Base, Francis Marion National Forest, Piedmont National Wildlife Refuge, and eight private properties in the Red Hills region.

The Ichauway RCW Population (measured by potential breeding groups, or PBGs) from 1999-2024.
The Ichauway RCW Population (measured by potential breeding groups, or PBGs) from 1999-2024.

Preceding the receipt of each batch of translocated birds, artificial cavity inserts were installed in mature longleaf pine throughout Ichauway. Translocated birds were released into a cavity insert and monitored over time for cavity fidelity and movement.

Most years have experienced a population increase, with increased observations of natural starts (initial attempts to make a cavity) and completed natural cavities in the past 6 years. In that same timeframe, management priorities have shifted from receiving translocated birds to relying on intra-population dispersals to “fill in” the remaining RCW habitat as we near cluster saturation.

A freshly installed artificial cavity insert.
A freshly installed artificial cavity insert.

Ripe Conditions for Decreased Nesting Success

In 2021, 2022, and 2023, fledgling sex ratios were skewed roughly 2:1 female to male. The trend of heavily skewed female fledglings resulted in many unoccupied clusters becoming active as birds dispersed in the fall. Because young females typically have a lower reproductive success rate, improving around age 3, a large influx of young females to the population for three consecutive years could result in decreased nest success in the subsequent years. Additionally, more females in the population could mean less “helper” availability for RCW pairs. Helper birds are almost exclusively 1–2-year-old males that remain with their natal territory, share the workload in cavity making and cleaning and assist in the nesting process.

The 2024 breeding season experienced a substantial increase in precipitation from the past two years, especially rainfall received overnight. The 2024 season experienced just shy of 24 cm of nighttime precipitation compared to 5.4 cm in 2022 and 6.6 cm in 2023 – an approximately 4-fold increase.

“I suspect overnight rain events could be strongly correlated with depredation and nest loss,” says Henshaw.

This “Achilles heel” of overnight rain events for RCW’s results in cavity displacement by kleptoparasites (particularly Southern flying squirrels) as well as nest abandonment if a cavity becomes flooded with rainwater. Henshaw frequently observed partially inundated cavities this spring. There are likely other energetic costs associated with colder, nighttime rain events.

“I previously associated all storms with direct nest loss, but I suspect there is something more to this in the timing and amount of rain. The last two years we have observed the same amount of depredation (9 nests), but if we look closer at the data, it seems the total number of rain events wasn’t as important as how much rain we received, and how much of that rain occurred at night,” says Henshaw.

This poses several questions about RCW behavior, especially as they age. Do older birds deal with rain better? Do young birds abandon nests more readily? Do young birds spend more (or too much) time foraging in the morning following a nighttime storm to recoup energy reserves that could ultimately cost the cluster their nest?

Henshaw atop a Swedish ladder during an RCW hatchling extraction.
Henshaw atop a Swedish ladder during an RCW hatchling extraction.

Moving forward to next season, Henshaw has some plans for focusing management efforts.

“We’ll probably scale back adding new clusters and focus more on cavity replacement and drilling [to encourage natural cavity making]. We want to prioritize strengthening the clusters we have established rather than adding clusters to the population next year.”

This year we may not have won the battle, but we are still winning the war to establish a resilient population of RCWs in our corner of southwest Georgia.

Learn more about The Jones Center at Ichauway’s Conservation program.

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