Final 2005 Mid-Summer Mute Swan Survey Results

Atlantic Flyway Council Snow Goose, Brant and Swan Committee

July 20, 2007, Portsmouth, NH

The 2005 Atlantic Flyway Mid-Summer Mute Swan Survey (AFMSMSS) was conducted during August and September 2005. All 17 AF states and the provinces of Ontario and Nova Scotia participated.  Methods include a mix of aerial and ground surveys.  Mute swans are counted by age class and the number of broods are noted.  During the 2005 AFMSMSS several states combined field operations to count mute swans with mute swan control work. 

Results:

A total of 13,649 mute swans were counted during the survey (Table 1).   The survey originated in 1986 and has been run 7 times at 3-year intervals during the last 20 years (Table 2).  This years count decreased slightly from the 2002 count, but was still the second highest on record.  Mute swan counts increased in each year of the survey except 2005 and the population shows a significant increasing trend (Figures 1 & 2).  Major factors that may cause decreasing numbers include, density dependent population growth, change in survey effort, or control programs.

Between 1986 and 2002 the survey counted between 9.8% and 12% young of the year.  Average brood size ranged from 2.8 to 3.8, averaging 3.3.  During the 2005 survey we counted 13.8% young and the average brood size was 3.5.  Percent young and brood sizes may be biased low as aerial surveys are not always able to distinguish adults and young.

Continuing Analyses:

The AFMSMSS data are being compared to trend data from the AF Mid-winter Waterfowl Survey (MWS), The AF Northeast plot survey, The U.S. Geological Survey (USGS) Breeding Bird Survey, and the Christmas Bird Count in collaboration with Dr John Sauer, USGS.  The utility and efficacy of each survey will be assessed.

Spatial analyses by county, state, and MWS flight segments will be explored, however, latitude-longitude coordinates for every observation will result in the finest scale density maps (Figure 3.)  Currently only NJ, MD, and VA collect lat-long for every observation.

Recommendations:

1)     Future surveys should include information on coverage and survey effort in each state to aid in interpreting results.  Simply standardizing the survey area is not sufficient if mute swans continue range expansion.

2)     Future surveys should also include information on control activities in order to evaluate the efficacy of those efforts.

3)     Comparisons with other mute swan surveys should be completed.

4)      Future surveys should include lat-log coordinates to allow production of an Atlantic Flyway mute swan density map.

Figure 3. Mute Swan densities in New Jersey during August-September 2005.