1. Effects of mycoplasmal conjunctivitis on the behavior of house finches
Erin Hotchkiss,
Sonia Altizer, Andy Davis, John Cherry
Dept. of Environmental Studies,
Emory University
Fall 2003

2. House Finch Carpodacus mexicanus
Native to southwestern North America
Few individuals were released in New York in 1940 and spread rapidly
Social flocks during fall and winter, feeder birds
Human-altered habitats
Altizer

3. Mycoplasmal conjunctivitis
Caused by the bacterium Mycoplasma gallisepticum
Found in domestic poultry
First sighted in winter of
Novel strain infects House
Finches
Easily recognizable symptoms
Has been known to infect other birds
Some recover, some chronically infected, some die
Direct transmission
Altizer

4. Disease spread rapidly through eastern North America
These interpolated maps from volunteer ‘citizen science’ reports show the rapid range expansion of Mycoplasma in just a few short years from the very first sightings. Here, the pink/red represents presence of diseased birds, and white represents areas where only uninfected house finches were seen.
Disease outbreaks started in the DC area in 1993, and by Nov 94 had spread into other mid-Atlantic states
By Nov 95, pathogen had spread mainly in a N-S direction; and then then farther west the following year (as shown in this map of Nov 96)
Thus, the disease spread so quickly that within 3 years after initial reports, infected birds had been sighted throughout much of their eastern range.
(Years 1 – 3 following initial case reports)
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5. House Finch abundance declined after
arrival of mycoplasmal conjunctivitis
Eastern VA, Eastern MD, DE 3 2
Birds/Hour 1
1970
1980
1990
2000
Central PA, Eastern NY
This pathogen caused a large and density-dependent decline in house finches, with numbers falling by up to 60% of what would have been expected in the absence of disease, and the lowest population levels were reported 2-3 years following disease invasion in a given area.
You see representative data here for house finch abundance in two mid-Atlantic regions -- Measured as average abundances from Christmas bird count
Has had been increasing prior to 1994 – evidence for logistic growth
Red points show annual abundance starting in 1994, when disease first struck
Instead of stabilizing or continuing to increase, HF abundance rapidly fell
Pattern was repeated at site after site after disease invaded, and sites where house finches had been more abundant experienced more extreme declines
The data shown extend to the end of 2000…
But even as of this winter there is no indication that House Finch populations have rebounded in the areas most severely affected. 10 8 6
Birds/Hour 4 2
1970
1980
1990
2000
Year
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6. Biology of the host and pathogen Collaborative approaches
Do epidemic patterns differ among regions?
What triggers fall/winter epidemics?
How do processes operating at the level of individual birds affect population-level processes?
Is host movement, reproduction, or social behavior important to disease spread?
Altizer

7. Behavioral Studies
Does infection status correlate with feeding efficiency and duration?
Is aggression or displacement related to infection status?
How many feeder ports are contaminated and later visited by house finches and other species?

8. Study Design Digital videotapes of feeder activity 4 – 14 October 2002
At least 50 individuals were observed
Behavior Tracker used to record feeding events
Score, sex, band, social interactions, feeding (pecks and seeds), flock sizes, duration of feeding bout, number of ports visited, reason for leaving

9. Effects of Infection on Flock Size and Feeding Duration
Infected birds had longer feeding bouts
Uninfected birds fed in larger mean flock sizes
compared to infected

10. Infection Status and Feeding
Efficiency (seeds/pecks) was much higher for healthy birds
Rate (seeds/sec) was also much higher for uninfected house finches
The total number of pecks per bout increased with infection
Total number of seeds eaten in a bout increased with infection as well (NS)

11. Aggression Mostly infected females displacing healthy males
Displaced
Displacers
Mostly infected females displacing healthy males
No instances of healthy finches displacing infected finches
G test and X2 test with p > x2.005 (d.f.=3)

12. Port Contamination
Average number of ports visited per feeding bout for finches with a score of “2” was slightly higher than “0” and “1” finches
More data needed

13. Implications Survival of birds infected with MG
Less efficient feeders and lower rates
Time wasted on social interaction
Smaller flock size
Longer duration at feeders
Uninfected house finches (and other bird species)
Displacement by infected birds
Contamination of feeders

14. Future Studies Compare vigilance of infected and healthy finches
The importance of seed handling time
Video data that is time-stamped for transmission study
Interactions with other bird species (especially those more vulnerable to MG)
Calculations of nutrition and energy expenditure

15. Acknowledgments
Thanks to Sonia and Andy for all of their ideas, help, and support
Thanks also to John Cherry for letting me take and add on to his house finch video data