Bendire’s Thrasher: New Mexico’s Highest

Scoring Species

Image: Dave Krueper Image: Cody Bear Sutton

Bendire’s Thrasher: Range

• Range map overestimates actual range

• Bendire’s Thrasher

does not occur in high elevation montane habitats throughout the depicted range

Image: Birds of North America Online

Bendire’s Thrasher: Population Estimates

• Partners in Flight Population Estimate: • 90,000 individuals • May not be highly accurate • Experts suspect the

population may be lower • NMDGF and USFWS

funded surveys from 2014-2016 and only found 57 breeding territories in NM

• New Mexico Responsible for ~ 28.7% of global population, according to Partners in Flight

Image: Matt Baumann

Bendire’s Thrasher: Population Trends

• Breeding Bird Survey Population Trends: • Rangewide:

- 4.57% per year since 1960s

• New Mexico: - 6.13% per year since 1960s

• 85% total population decline

• Caveat: data based on small sample size

Image: USGS Breeding Bird Survey

Bendire’s Thrasher: Population Trends

• Partners in Flight half-life research estimates another 50% decline in 18 years

• On Partners in Flight Red List

• Only 19 bird species on

the Red List Image: USGS Breeding Bird Survey

Bendire’s Thrasher: Habitat Needs

Image: Birds of North America Online

• Occupy lower elevation habitats including:

• Soaptree yucca grasslands

• Mesquite savannah

• Juniper savannah

• Do not occupy dense shrub

thickets or montane areas

Bendire’s Thrasher: Habitat Needs

Image: Cody Bear Sutton

• Research funded by NMDGF and conducted by Dr. Martha Desmond and Cody Bear Sutton at NMSU

• conducted from summer 2015 to summer 2016; results expected summer 2017

• Investigating territory-scale habitat needs of breeding Bendire’s Thrasher in NM and AZ

Bendire’s Thrasher: Habitat Needs

• Preliminary results suggest Bendire’s

Thrashers need approximately 40% cover of shrubs; shrubs over 5 ft in height are statistically important

• Structure appears to be more important than specific plant species • They use a variety of shrub

species including soaptree yucca, mesquite, juniper, tamarisk, and joshua tree

Images: Cody Bear Sutton

Bendire’s Thrasher: Threats

Image: Matt Baumann

• Hypotheses Regarding Causes of Decline:

• Overgrazing • Agriculture • Tall shrub removal • Drought and Climate

Change • Invasive grasses • Off-road vehicle use • Competition with Curve-

billed Thrasher

Bendire’s Thrasher: Threats

• Suspect overgrazing, tall shrub removal, and drought may be primary causes of decline in New Mexico

• Caveat: need research to confirm or deny this

Image: Wild Sonora

Bendire’s Thrasher: Threats

• Research, and anecdotal evidence, suggests Bendire’s Thrashers primarily eat insects on the ground

• Ground-dwelling insect abundance is likely reliant on forb

growth • Forb growth is likely reliant on adequate rains, and is

probably impacted by overgrazing

• Moisture was the most important variable in predicting occupied habitat in a Maxent GIS model created by Kurt Menke and funded by NMDGF

Images: Insects Unlocked (left) and D.K. Find Out (right)

Bendire’s Thrasher: Threats

• Recent research suggests Bendire’s Thrashers need ~40% cover of shrubs, and shrubs over 5ft in height are statistically important

• Large shrubs may be removed for grazing and agriculture

• While overgrazing sometimes results in shrub invasion, they likely grow in too thick (>40% cover)

Photo: Cody Bear Sutton

Bendire’s Thrasher: Threats

• Suspect Bendire’s Thrashers evolved to select breeding territories based on limited tall shrubs

• However, due to overgrazing and drought, they may not be successfully reproducing on overgrazed desert grasslands and savannahs

• Just because they are found on overgrazed lands does not mean this is what they need, or that they are successful in overgrazed areas

Image: Cody Bear Sutton

Bendire’s Thrasher: Threats

• Many Bendire’s Thrashers have been found along roadsides where there is likely more moisture, more forb growth, and taller shrubs

• Many Bendire’s Thrashers are found on Arizona “Ranchettes” where there is likely overgrazing, but where there are probably also areas with tall shrubs and good forb growth (around the houses, etc.)

• Caveat: above items are anecdotal

Bendire’s Thrasher: Threats

Image: USGS Breeding Bird Survey

• Areas where the Bendire’s Thrasher population appears to be increasing include “ranchettes” near Tucson and Phoenix, as well as National Wildlife Refuges, National Parks, and National Monuments

• All of the above likely have

limited to no grazing

Bendire’s Thrasher: Threats

Image: Christina Kondrat-Smith

• The good news: • Bendire’s Thrashers

appear to tolerate human presence (on left is a “ranchette” where they were documented in AZ)

Bendire’s Thrasher: Threats

Image: Christina Kondrat-Smith

• Bendire’s Thrashers appears to do well if grazing practices are only slightly improved and some tall shrubs are retained

• Joshua Tree Important Bird Area (pictured) in Arizona was designated due to high numbers of breeding Bendire’s Thrashers

• This area appears to have been heavily grazed in the past and is now recovering; it is still currently grazed, but likely at lower levels

Bendire’s Thrasher: Management Actions

• Recent GIS analysis suggests the Bendire’s Thrasher range in NM consists of:

• Private land: 35% • BLM land: 24% • Tribal land: 18% • State land: 17% • Forest Service land: 2% • Other agencies that have

less than 0.01% each

Image: Birds of North America Online

Bendire’s Thrasher: Management Actions

• Farm Bill funds can be used to encourage wildlife-friendly grazing practices

• Private and tribal landowners are eligible for funds, as well as holders of grazing allotments on public land

• This means ~96% of range in NM could benefit from Farm Bill funds

Bendire’s Thrasher: Management Actions

• The NRCS Regional Conservation Partnership Program funded: • 8 million dollars for Cerulean

Warbler habitat work • 5 million dollars for Golden-

winged Warbler habitat work • Current information suggests

Bendire’s Thrasher is doing worse than both of these species

Image: Glenn Bartley

Image: Rick and Nora Bowers

Bendire’s Thrasher: Other Species That May Benefit

• Management for Bendire’s Thrasher may benefit a variety of other bird and wildlife species including: • Scaled Quail

• Loggerhead Shrike

• Gray Vireo

Image: Larry Selman

Image: Tom Johnson

Image: Gerrit Vyn

Bendire’s Thrasher: Current Research

• Very little research has been conducted on Bendire’s Thrasher

• Research on habitat needs from 2015-2017 in NM and AZ; funded by NMDGF and conducted by NMSU; volunteers provided by Tucson Audubon

• Surveys and habitat use research in 2017 in AZ, NV, and CA; funded by the BLM

Image: Innovation Excellence

Bendire’s Thrasher: Needed Research

• Additional habitat use studies needed

• Research investigating grazing and its potential impacts on production

• Research investigating other potential causes of decline

• Surveys designed to obtain a more accurate population estimate

• Distribution and habitat needs on wintering grounds in Mexico

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Bendire’s Thrasher: Important

Take-Home Points

• Research priorities include figuring out the primary causes of population decline and figuring out distribution and habitat needs on wintering grounds

• Given the apparent rapid rate of decline, recommend on-the-ground conservation measures be implemented as soon as possible

• Farm Bill conservation programs offer a large amount of money to potentially improve habitat Image: Clipartfest

Questions????

Image: Dave Krueper