Print PageThe Rocky Mountain populations of Sandhill cranes (Grus canadensis) have become popular in their spring migrations to the San Luis Valley of Colorado, providing people with a glimpse of these majestic birds. More than 20,000 Sandhill cranes gather in the spring to feed on left-over grains in fallow agricultural fields to store enough energy for their migration north. Hundreds of people visit the Monte Vista National Wildlife Refuge during an annual spring Crane Festival, driving through pullouts designated for crane viewing. Despite the frequent interactions between the public and cranes, no one has researched the potential impacts the human visitors have on cranes. The following questions guided this research’s goals and objectives:
1. What is the percent time cranes spend in vigilance postures, foraging, spreading or folding wings, flying and facing toward or away from the pullout as the rate of visitors to the refuge pullouts increase?
2. How does the percent time for crane positions differ on the refuge-prepared agricultural fields with pullouts versus the private fields without pullouts?
We began by collecting data on visitors and Sandhill cranes at three refuge sites with pullouts, and one private field with no pullout. Visitor and crane observations began simultaneously and were collected at five minute intervals. Every five minutes, one team would record the numbers of people inside and outside their cars, as well as car types. Another team used focal animal sampling to monitor individual cranes with a spotting scope for five minutes, cataloguing each time the cranes changed position. Positions included foraging, vigilance postures, spread and folded wings, flight responses, and crane orientation to the pullout.
Results/Conclusions
The sample size included 144 Sandhill cranes. The Proc GLM procedure returned no significant differences (based on α=.05) between sites for the percent time cranes spent in disturbance postures, which included vigilance (F-value=.53, p-value=.6628), spread wings (F-value=2.33, p-value=.0772), and flying away (F-value=.99, p-value=.4018). We also used Spearman correlation coefficients (Rho) to correlate visitor data with the crane behavior. Results revealed one significant correlation between the rates of people outside their car and the percent time cranes spent with their wings spread (Rho=.69775, p-value=.0116) at the marsh site on the refuge. The data did not show clear trends and most correlations were not significant. These results indicate that the Sandhill cranes could be habituated to human visitors during their spring migration to the San Luis Valley.
