Using Bioenergetics and Radar-Derived Bird Abundance to Assess the Impact of a Blackbird Roost on Seasonal Sunflower Damage

Methods aimed at reducing avian damage to agricultural crops are routinely implemented in situations where efficacy can be assessed by quantifying blackbird (Icteridae) abundance relative to environmental variables and extrapolating to ensuing crop damage. Concomitantly, Weather Surveillance Radar (WSR) data may have potential to enhance crop damage mitigation through improved monitoring of nuisance wildlife populations. We used WSR to derive daily abundance estimates of blackbirds at a fall roost in North Dakota, USA from 2012 to 2019. We integrated these estimates with previously developed bioenergeticseconomic models to estimate local sunflower (Helianthus annuus) damage. The greatest losses usually occurred during a brief period in October, when peak blackbird abundance coincided with large percentages (>50%) of mature but unharvested sunflower fields. Most sunflower fields were harvested later than peak blackbird abundance (360,000–1,120,000 birds) and maximum daily damages ($900–$2,000 USD per day). This seasonal trend suggests advancing harvest time as a strategy to avoid the greatest losses in yield (up to $1,800 in savings at this 1 roost), which may be attainable by earlier planting of early-maturing crop varieties or crop desiccation.