The Rouge River Bird Observatory bands birds on the campus of the University of Michigan-Dearborn (42.3183,-83.23315). Banding is done primarily during migration seasons. From 1993-2007 banding was done in both spring (April 15 to June 5) and fall (August 15 to November 5) migrations. Since 2007, banding has only taken place in the fall.
RRBO operates the equivalent of approximately 20 twelve-meter mist nets in three adjacent habitats: an open, weedy field; a shrub area dominated by dogwood and buckthorn; and inside a forest edge. Areas are maintained to limit succession.
It is believed that inland sites such as the campus of UM-Dearborn provide important information on how birds choose stopover sites versus coastal sites that tend to concentrate migrants regardless of habitat quality. Birds may select appropriate habitats and stay at a site only if there is potential for them to gain mass, and should move on quickly if a site does not have adequate resources. While the number of birds captured is lower at a site like RRBO’s, we have gained valuable insight into how birds use urban stopover habitats. You can read more about this focus of our research here.
Weather permitting, nets are opened at dawn and stay open for a minimum of four hours, and are checked every 20 to 40 minutes.
Three weather variables factor in to whether or not RRBO bands on any given day: precipitation, wind, and temperature.
Precipitation: We do not band in any sustained precipitation, including light drizzle or mist that last more than one hour, or if any sustained precipitation is forecast or seen approaching on radar. When birds become damp or wet, including from wet nets, they can easily become chilled and stressed, even in fairly warm temperatures, especially if there is a breeze.
Wind: Generally, RRBO does not keep nets open in wind speeds much above 10 MPH, depending on the wind direction and temperature. Any wind above 15 miles an hour certainly presents danger to birds in most situations. As nets move about in the wind, they can easily pull and strain, dislocate, or break wings or legs, or in some cases strangle birds. This is especially true of small birds such as warblers and kinglets. While these cases might be uncommon in wind speeds of 10-17 MPH or so, we don’t feel it’s worth the risk.
Temperature: Unless nets can be monitored nearly constantly — and in our case the nets are not where they can be under continual surveilliance — banding in temperatures below 40F requires careful consideration of wind speed and cloud cover (how quickly temperatures will rise). RRBO rarely bands in temperatures below 40F. High heat, especially when combined with direct sun, will also be grounds for closing.
Our goal is not to see how many birds we can catch. We focus on mass gains and condition of birds, and stressed birds are probably more likely to be recaptured (or die and never be recaptured), thus introducing bias into our results. Therefore, we avoid banding in poor conditions and our experienced banders strive to process birds quickly and safely.
How we calculate capture rate
In order to compare different locations or years that may operate the same number of hours but with more or fewer nets, capture rate is calculated by “net-hours.” One net hour is one 12-meter net open one hour, or two 6-meter nets open one hour, etc. This rate is often expressed per 100 net-hours for more manageable numbers.
Use the links on the right to find out more about the RRBO banding program.