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

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

Mycoplasmal conjunctivitis Caused by the bacterium Mycoplasma gallisepticum Found in domestic poultry First sighted in winter of 1993-94 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

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) Altizer

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 Altizer

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

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?

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

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

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)

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)

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

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

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

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