Avian Acoustic Monitoring - Spring and Fall 2013

Avian Acoustic Monitoring - Spring and Fall 2013

June 2, 2014

This report summarizes the 2013 avian acoustic monitoring efforts for spring and fall
migration.

Avian Acoustic Monitoring: Spring and Fall Migration 2013 Debbie Leick Kate Stone

Table of Contents

This report summarizes the 2013 avian acoustic monitoring efforts for spring and fall migration. When we analyzed the nocturnal flight call data, we observed spatial and temporal patterns between monitoring sites and seasons.

The audio review followed the same methods used for the fall 2012 pilot study. We used automated software detectors (Old Bird, Inc.) to extract “tseep” and “thrush” calls.

“Thrush” detects mid-frequency calls from many species including American Robin (above), Catharus thrush, shorebirds, and Western Tanager (below). After running the detectors, we reviewed the results to eliminate false positives, noise, and duplicate call files.

Though we accumulated more “tseep” than “thrush”, we detected few nocturnal flight calls in the spring. Despite the low numbers, temporal and spatial trends appear in the data.

Compared to spring migration, we extracted more fall nocturnal flight calls. The plotted data show temporal and spatial patterns.

When we compared total flight calls between fall 2012, spring 2013 and fall 2013, we found more activity in the fall than in the spring (Figure 5). Detections also increased between fall 2012 and fall 2013.

Forest fire smoke filled the valley in September 2012. Smoky inversions reached the higher elevations on many days. Did this cause a shift in nocturnal migrants’ routes or flight altitudes?

We detected more calls in 2013, but in both years most detections occurred at the beginning of the season.

No clear patterns exist between fall 2012 and fall 2013 for weekly “thrush” detection totals.

Fall migration 2012 and 2013 weekly Ridge “thrush”.

The table, below, lists the current and proposed avian acoustic monitoring projects for 2014. This spring and fall, we plan to continue nocturnal flight call monitoring at all three sites to see if spatial and temporal trends persist.