We’re back with our latest installment of Leopold Live!: Chapter 2 at the Selah, Bamberger Ranch Preserve, and we greatly enjoyed connecting with you to talk about wildlife management techniques. In this episode we spoke with the Bamberger Ranch’s resident ornithologist, Christina Farrell, about cowbird trapping and how it can be used to benefit native bird species on your property. Under the wildlife tax valuation program in Texas, cowbird trapping is listed as a qualifying management practice in the predator control category. But why? First we need to dig a little bit into the natural history of this species.
In the past these species followed the large herds of American bison as they moved across the plains so they did not stay in any one place for a long period of time, especially not long enough to build a nest, lay eggs and raise young. To solve this problem, they evolved a unique life history strategy and became what we call “brood parasites.” This means they do not build their own nests or care for their own young, and instead place this burden on a host species.
Historically, this was not an issue as cowbirds were constantly migrating with the bison and were not able to parasitize any one area too heavily. All this changed with the settlement of people and their livestock, particularly cattle. It meant cowbirds were able stay in one place, heavily parasitize other species’ nests, and ultimately have a detrimental effect on resident songbird populations.
This is where we as wildlife stewards can make a difference by trapping cowbirds. The Texas Parks and Wildlife Department has a program with resources and technical guidance dedicated to helping landowners manage this species. Many of the participants in this program reside in the Edwards Plateau as this region is home to several species of conservation concern in Texas. The only dates you can operate traps are March 1st-May 31st.
Since this technique involves dealing with live animals, protocols have been developed to ensure they are handled safely and responsibly throughout the trapping process. This includes data collection of the trapping dates, cowbird trapping numbers (including the numbers of males and females trapped), non-target birds trapping numbers and banded bird numbers. Finding a banded bird is quite a rare event so if you do happen to catch one be sure to document its unique 9-digit band code before releasing it and report it to the USGS Bird Banding Lab.
Next we dug a bit into the different types of traps available for trapping cowbirds. Christina mentioned that the one they use on the ranch is a portable metal trap and described how it works well for their management. No matter which trap design you decide to go with, they will all have similar functions and location requirements. Christina said her ideal trap location is close to livestock (since this is what attracts your cowbirds to the area), in an open grassland area, accessible for ease of checking on and maintaining the trap, and on level ground.
Now you’ve picked a trap location, what are the essential items to make it operational? Christina mentioned that you will need to always have food and water available. In addition, you’ll want some shade on your trap to give birds the option to get out of the sun. Another important factor is the weather. If it looks like it’s going to be very rainy or windy Christina recommended not operating the trap as this can greatly stress trapped birds. Lastly, it’s always a good idea to start your trapping with 10-15 birds in the trap (if possible) as cowbirds are a curious and social species and so will be more likely to enter the trap.
After you have trapped some birds, Christina recommended using a net from outside or inside the trap (whichever you are more comfortable with) to capture individuals. Once you have the bird in hand, we recommend dispatching them through cervical dislocation as this is the safest and most humane method for euthanasia.
Christina mentioned that you will want to make sure your trap is not easily accessible to predators as we do not want trapped birds to be injured or killed by them. Some best practices include making sure the trap is not accessible to digging mammals, keeping the grass low to be able to keep an eye out for snakes and treating the area for fire ants. Lastly, we talked about shutting down your trap when it’s not in use. This includes ensuring the entrances are completely sealed shut to keep birds out or completely opened to allow birds to escape.
We rounded the episode out with a short Q&A session with Christina.
What should I do if I find an unhealthy or diseased bird in my trap?
Christina recommended dispatching it using cervical dislocation and incinerating it. This will ensure no other individuals can come in contact with the diseased animal and prevent any potential spread of the disease.
Should I record all non-target species I find in my trap?
Absolutely! Christina recommended documenting all non-target species and how many were trapped before releasing them.
How many traps should be placed per acre? How many are operated on the ranch?
Christina did not have a rule of thumb for number of traps/acre, but she speaks more the latter of these questions. On the ranch they operate two cowbird traps since this allows them to be able to check them every day. Having fewer allows them to ensure that their traps are always operating perfectly and are very safe for the birds. Christina recommended to err on the side of caution, which usually means fewer is better as this will let you be able to better check and maintain them.
Leopold Live!: Chapter 2 is off to a great start, and our crew can’t wait to share our next episodes with you! Keep an eye on Facebook for upcoming episodes in the new year.