North Coast and Cascades Network landbird monitoring: Report for the 2021 field season

Holmgren, Amanda; Wilkerson, Robert; Siegel, Rodney; Ransom, Jason

doi:10.36967/2294618

The North Coast and Cascades Network (NCCN) continued to implement the Network’s Landbird Monitoring Protocol in 2021, in partnership with The Institute for Bird Populations. The protocol was initially field-tested with data collected from the annual panel only, as part of protocol development during 2005–2006, and has subsequently been implemented fully (including data collection on the annual panel as well as five alternating panels) for the past 14 years (2007–2021), except for 2017 when data collection was temporarily suspended to reallocate resources for a 5-year data synthesis. In 2021, we conducted 1,167 point counts at point count survey stations along 68 transects in the large wilderness parks of the NCCN, including Mount Rainier National Park (MORA), North Cascades National Park Complex (NOCA), and Olympic National Park (OLYM). We also conducted 54 point counts at San Juan Island National Historical Park (SAJH), including 38 at American Camp and 16 at English Camp. Across the three large parks, we documented the presence of 135 species and one hybrid, 94 of which were detected during point counts. For 57 species (all species for which we amassed at least 91 point count detections over the period 2005–2021), we present the total number of detections of each species on each park’s annual panel transects during the 2005–2021 field seasons. We caution, however, that these detection totals have not been adjusted for differences in survey effort, observer effects, or potential differences in detectability of birds between years; such adjustments will be made in conjunction with trend analyses in a future multi-year report. The number of bird detections on annual-panel transects across all three large parks increased by 1,058 between 2020 and 2021, though the magnitude and direction of the change in detections varied among the parks. At both MORA and OLYM detections increased between 2020 and 2021. When factoring in the number of point counts conducted each year, both parks saw a substantial increase in the average number of birds per count (an increase of 32% at MORA and 16% at OLYM), though these detection rates were more similar to those of 2019. At NOCA there was actually a decrease of 296 detections on annual-panel transects, a decline of about 10% from 2020. Some of the overall increase in bird numbers across the Network is due to a high number of red crossbill detections in 2021, particularly at MORA and OLYM. We detected them at higher numbers in both of these parks than in any of the previous 15 years. Several other species were also detected in slightly or moderately greater numbers in the three large parks in 2021 than in previous years. Overall, warbler detections were high, but Nashville, yellow-rumped and black-throated gray warbler in particular had higher numbers of detections than in any year since the start of the monitoring program. Interpretation of these results will be completed as part of the next multi-year trend analysis, which will account for annual variation in survey effort, observer effects, and detection probability.

North Coast and Cascades Network landbird monitoring: Report for the 2021 field season

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