Nest Microhabitat & Reproductive Success of the Mountain White-crowned Sparrow

Brett Klaassen Van Oorschot, Ondi Crino, and Creagh BreunerUniversity of Montana

Mountain White-crowned Sparrow (Zonotrichia leucophrys oriantha)

Mountain White-crowned Sparrows as a study system

Question:Does nest microhabitat affect the reproductive success of these birds?

Brand-new fledgling

Context for Research

(Google 2009)

Tioga Pass: the field site

• Nests are built in a wide range of microhabitats.

• Over half of all nests fail, but ecological consequences are unknown.Specific Questions:

1. Does the vegetation surrounding the nest affect fledging success?

2. Does the vegetation surrounding the nest affect nestling condition?

Background

Belding’s Ground Squirrel(Spermophilus beldingi)aka “Sage Rat” or “Picket-pin”

Fearsome and elusive predator of the Mountain White-crowned Sparrow.

Background

• Nests are built in a wide range of microhabitats.

• Over half of all nests fail, but ecological consequences are unknown.

Specific Questions:1. Does the vegetation surrounding

the nest affect fledging success?

2. Does the vegetation surrounding the nest affect nestling condition?

Background

Nest Searching….

Tioga Pass Meadow A well-hidden nest

Morphological Measurements

Ondi Crino taking chick measurements Six-day-old nestling

Habitat Assessment

Nest location

Short-hand sampling

• Measured 2m in each direction • Vegetation type and structure• Ground water availability• Nest height and aspect• 1777 individual samples with

over 26,665 possible datapoints for 37 nests.

•Does the environment surrounding the nest affect fledging success?

•Does it affect individual nestling condition?

Nestlings waiting for lunch

Questions, revisited

Principal Component Analysis

• Four main components in nest microhabitat

•PCA reduces variables to a few key factors

•Components inferred from correlations among variables (e.g. height & density)

•Relationships between vegetation were also common: More Lodgepole Pine means less Yellow Willow

Results

No significant effect of vegetation on fledging success

p=0.40 p=0.97

p=0.93 p=0.70

Nestlings raised in tall vegetation are lower condition

Results, cont.

Nestling condition improves as season goes on

(June 14) (July 14)

Results, cont.

Nest vegetation height causes decrease in conditionregardless of date

p=.03

Results, cont.

• No effect of nest habitat on fledging success.

• Nests habitat is a poor predictor of fledging success.

• Sparrows on the ground and in willows or pines are equally likely to experience abandonment or predation.

• This data supports the idea that predation is random.

Discussion

Discussion

• Nests built in tall vegetation have lower-condition nestlings.

• Difficult for parents to get into nests?

• Foraging occurs away from tall vegetation, leading to less provisioning?

• More time spent guarding or thermoregulating?

• Nestling condition increases with date.

• Food availability (bugs & open ground) increases over breeding season.

• Indicates trade-off between early mating and nestling condition.

Ending Thoughts

•Mountain White-crowned Sparrows offer a unique opportunity to explore the consequences of nest ecology.

•Understanding ecology will help explain life-history, behavior, and physiology.

•Future directions include looking at generational effects on nesting behavior and ecology at other nesting sites.

Ondi CrinoCreagh BreunerThe Breuner LabDoug EmlenBill HolbenPaul AlabackArt WoodsTom BassettJen SmithBret TobalskeUniv. of Montana MILES ProgramHHMI

Questions?

Acknowledgements & Questions

US FWS