Case Study: Nesting Gull Colony Management in Milwaukee

Site Overview

This academic institution is located in the Greater Milwaukee area.

Ring-billed Gull Colony Moves In

In 2014, a Ring-billed Gull colony of approximately 6,000 birds moved into the heart of the campus during the nesting season. Rooftops were so congested with feces, feathers and dead birds that air ducts, air return filters and drains were all clogged. Much of the feces, debris and juvenile gulls also made its way down to the ground, putting staff and students in harms way. The condition was so bad that maintenance staff could not access many components on the rooftops, requiring pressure washing multiple times a week. Droppings on windows need a lift to be cleaned properly.


Gull Egg Depredation

In 2015, Migratory Bird Management (MBM) was hired for egg depredation with the goal of removing all the eggs over the duration of the nesting season. MBM acquired the federal permit needed to remove eggs for the customer and submitted the gull egg depredation permit report after the season had concluded. The company then successfully removed over 8,000 Ring-billed eggs and nearly 450 Herring Gull eggs. As a result, there were no juveniles running around, no dive bombing birds and the colony proceeded to leave in early July.


Continued Egg Depredation

In 2016, the Ring-billed colony returned, however, heavily diminished. MBM removed just over 1,800 eggs and the colony took off earlier than the year prior. In 2017, the number of eggs removed again drastically dropped to 444. 2018, the last year of any trace of Ring-bills saw only 252 eggs and a departure in May. The Ring-billed colony has not returned since.


Figure 1. Number of gull eggs removed throughout the duration of MBM’s service.

Herring Gulls

While Herring Gull numbers are not nearly as high as the Ring-billed colony, these bigger, more aggressive gulls can do an equal amount of damage in various ways. The Ring-billed colony was more concentrated, while Herring Gulls are spread out all over campus. This means that students and faculty are at much greater risk of more aggressive attacks than the Ring-billed Gulls. Rooftops that MBM has consistently serviced since 2015 have seen a significant drop in egg totals. The increase in eggs taken each year is from an increased number of buildings being serviced, resulting in a campus-wide effort.


Over 6 years of gull management, nest and egg counts have dropped over 75%. Ring-billed Gull egg depredation proved to be successful within the first 2 years, as majority of the colony did not return the following year after egg removal began. The Herring Gull species, while more aggressive than Ring-billed Gulls, are also more resilient. They will pursue nesting opportunities on a property over an extended time, potentially bouncing rooftop to rooftop to avoid harassment. The MBM service program adapts to that resiliency, resulting in a steady decline year-to-year as egg depredation continues into 2021.