The Red-Cockaded Woodpecker

The red-cockaded woodpecker (RCW) is an endangered species endemic to the Southeast United States. This project aims to evaluate patterns regarding RCW distribution, the ecological importance of the species, as well as the conservation potential of the species.

The two patterns in RCW distribution are:

1. The relationship between long-leaf pine density and RCW habitat spread.
2. The age of long-leaf pine trees and RCW foraging habits and cavity excavation.

There are four main papers referenced throughout this storymap. A brief summary of the papers are included below.

• DeMay and Walters 2019: An evaluation of the change in timing of RCW breeding and reproduction in response to global warming and changing precipitation patterns. Evidence shows that RCW reproduction occurs earlier in spring because it warms quicker and that reproduction that occurs earlier tends to be more successful. In springs where there is a high amount of precipitation, reproduction is delayed and these breedings are less successful. The data demonstrates the effects of human-induced climate change on the RCW.
• Macey et al. 2016: The authors study the foraging habits and habitat selection tendencies of the RCW to identify ideal foraging domains and habitat. They found that the factor having the most negative impact on foraging habits and habitat selection is the hardwood midstory area. Other factors include canopy closure and density, midstory density, and shrub height. This information is important in identifying ideal RCW habitat patterns.
• RAMIREZ and OBER 2014: The authors analyze RCW nest site selection in order to determine the habitat characteristics and land management activities that contribute to high RCW productivity. The data demonstrates that the number of annual fire events was most important to habitat selection and cluster density was most significant in reproduction success. This data informs conservation actions by highlighting the importance of fire regimes in long-leaf pine ecosystems.
• Walters 1991: The author of this paper reviews the biology of the RCW, including habitat requirements and social interactions. The author references these biological aspects of the RCW in order to inform conservation practices that can be implemented to preserve this species.

The two important factors determining RCW distribution patterns in long-leaf pine forests are the density of long-leaf pine trees in the ecosystem and the age of the trees (RAMIREZ and OBER 2014).

• Tree age and cavity excavation: Older and recently dead long-leaf pine trees have a higher chance of contracting heart rot, a disease that softens the inner tissue (U.S Fish and Wildlife Service 2020). This makes it easier for the RCW to excavate cavities for nests. Therefore, RCW prefer mature trees because it takes less time and energy to excavate a softened tree.
• Tree density and foraging habits: The RCW preference for less dense forest can also be explained by the effects of tree density on insect populations. Dense midstory forest layers prevent light from reaching herbaceous plants near the forest floor, which insects depend on (RAMIREZ and OBER 2014). RCWs favor foraging area that is less dense forest because the insect populations are generally higher in those areas.
• Tree density and reproduction: These woodpeckers have a very unique social interaction involved in their reproduction cycle. The live in groups of 2-6 that consist of the breeding male and female, as well as between 0 and 4 "helpers" that are typically younger male RCWs (Walters 1991). These helper birds assist in egg incubation as well as food collection for the offspring. They rarely disperse far away from the breeding pair to start reproducing on their own, so they require their own nests in the same territory, in a 5 acre radius from the original cavity (Walters 1991). Research has found that the birds tend to spread throughout this radius, in a small density (Walters 1991).

The RCW was considered common around 300 years ago, before European settlement, timber harvesting, and land clearing in the Eastern United States. At this time, around 1 to 1.6 billion of these woodpeckers inhabited 90 million acres of lone-leaf pine ecosystem.

The current RCW range spans most of the Southeastern U.S., but has become increasingly patchy as land clearing and logging continue to fragment RCW habitat. The majority of RCWs can be found in Florida, Texas, and along the coasts of South Carolina and North Carolina.

The map below demonstrates the range of the RCW in the United States as of 2020 and where the woodpecker is possibly extinct (B.L. 2020). It is a better way to visualize the losses in RCW range since the 1700s.

The IUCN red list is "the world's most comprehensive information source on the global conservation status of animal, fungi, and plant species," (IUCN 2020). This list assesses the status of species around the world to determine the threat level that species is facing. The RCW was listed as "endangered", but was recently down-listed to "near threatened". However, IUCN data shows that RCW population numbers continue to decrease. This suggests that they should be up-listed back to "endangered".

The IUCN details a variety of human impacts on the RCW and its habitat. This list includes:

Some of the impacts listed on the IUCN website are widespread effects of human-induced environmental change.

• Climate change: Global warming and rising temperatures has effected the reproduction cycles of the RCW. Research shows that increasing spring temperatures has caused advanced nesting and advanced nests were more productive than later nests (DeMay and Walters 2019). In addition, areas with higher spring precipitation levels saw delayed nesting and less productive nests (DeMay and Walters 2019).
• Severe weather (storms, flooding, etc): Increased severe weather patterns are a result of climate change and they cause more stress and disturbance to long-leaf pine ecosystems.

The direct and indirect impacts of humans negatively impact the already small and fragmented populations of the RCW in the Southeast United States. RCW populations' geographic isolation from other populations, coupled with these human stressors, increases the probability of sub-population extinctions.

Red cockaded woodpeckers are critical to their ecosystem due to their role as a keystone species and ecosystem engineer.

A keystone species is a species that has a large effect on a community despite its relatively low biomass.

RCWs are considered a keystone species in long-leaf pine ecosystems because many other species depend on RCW cavities. These organisms are called 'secondary' nesters use their cavities after they have been abandoned or "steal" them from RCWs (Walters 1991). This contributes to higher species richness in the community. 27 species of vertebrates have been recorded using RCW cavities including: lizards, squirrels, snakes, and other bird species. Without RCW present in the community to create cavities, other species cannot survive.

Trophic cascades are powerful indirect interactions that have the potential to control ecosystems. In the absence of RCWs, a trophic cascade could occur because there would be no organisms to create cavities. This would negatively affect the populations of any species that depend on the cavities or that feed on the woodpeckers. It would throw a wrench in community dynamics and decrease overall diversity of the ecosystem as it would no longer be able to support a variety of species that depend on the RCW.

An ecosystem engineer is any organism that creates, modifies, or maintains an ecosystem.

RCW excavation of cavities qualifies this species as an ecosystem engineer. RCW maintenance of cavities maintains the long-leaf pine forest ecosystem by sustaining the RCW and the other species that depend on the cavities for shelter and offspring rearing.

It is important to note that the concept of keystone species and ecosystem engineer are not the same, even though the overlap. An ecosystem engineer can be a keystone species, but that is not always the case.

RCW are an "umbrella species". Species are considered an umbrella species when the protection of that species indirectly promotes many other species. By protecting the RCW, species that depend on RCW cavities are also protected. This woodpecker's status as an umbrella species makes it extremely important in conservation. If populations of RCW continue to decline, the species dependent upon this bird will decline as well. If we fail to protect RCW now, we may start to lose even more species.

The IUCN website outlines conservation actions that have been taken by the U.S. government in order to protect RCWs.

The conservation actions listed are well supported by research showing that habitat selection patterns and productivity of the RCW are strongly influenced by fire patterns, the distribution and maturity of long-leaf pine trees, as well as the density of midstory vegetation.

Many of the conservation projects in place for the RCW have been successful in maintaining current populations (B.L. 2020). The continuation of these projects is essential to the survival of the RCW and the species that depend on it.