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November 17, 2023

Although we may feel worlds apart, we are connected by migratory birds. In turn, migratory birds are connected to us and directly affected by our actions.  

Lili Chavarria-Duriaux, a woman, banding a red and black bird, white-winged tanager (Piranga leucoptera).
Lili Chavarria-Duriaux, operator of the MOSI (Monitoring Overwintering Survival) station at El Jaguar Reserve in Nicaragua, banding a white-winged tanager (Piranga leucoptera). 
Dona Lili has coauthored two field guides to the birds of Nicaragua and was the recipient of the 2018 Partners in Flight Public Awareness Award. 

Bonnie poured herself another cup of sustainably grown coffee from Nicaragua and inhaled the rich aroma. The morning news softly droned in the background with tales of the Green Bay Packers draft picks. As she pondered her upcoming lunch with friends, she heard a loud thump on her kitchen window and saw feathers stuck to the glass. She hurried outside to investigate. On the ground lay the most beautiful bird she had ever seen in her 80 years of Wisconsin living. His black mask was striking next to his yellow cap and wings. Until that morning she had never realized she was living among such splendid, colorful birds. Her heart sank as she realized this beauteous golden-winged wonder no longer shared her world because of a simple thing: her window. Bonnie immediately decided to do whatever she could to stop future bird collisions with her windows and tell her friends to do the same!  

That same morning, but almost 2,000 miles away on a former Nicaraguan coffee plantation, Liliana Chavarría-Duriaux, pondered the preparation of her season’s bird banding data. Often referred to as “Dona Lili,” she is a leader in Central American bird research. Almost three and a half years earlier, Dona Lili had held and admired that same, beautifully masked bird as she attached a small numbered, silver band to his tiny leg in El Jaguar Reserve, a private reserve in the cloud forest of Nicaragua. 

Every migratory bird that strikes a window is an unfinished story. Their spring songs are silenced, their bright jeweled feathers are absent, and the next generation is lessened. However, because this bird was banded, we can learn more about its life before it was lost to window collision.  

A Golden-winged Warbler, a yellow, black, and gray songbird, with a silver metal band on its leg, struck a residential window
A banded Golden-winged warbler, that died as a result of a window collision.                    



Reports of banded birds that have collided with windows are not uncommon for the U.S. Geological Survey’s Bird Banding Lab, the agency that manages bird banding in North America in coordination with the Canadian Wildlife Service’s Bird Banding Office. However, the loss of this particular bird immediately caught the attention of Bird Banding Lab staff; it was the first time a banded golden-winged warbler was reported to have hit a window and this species is in trouble, with severe population declines across its range.  

Bird banding data is rich with details that give us a better picture of this bird’s life from when it was banded by Dona Lili to when it was recovered by Bonnie. Because Dona Lili banded this individual as an adult bird, we know that he was at least five years old at the time of the collision. 

Through the banding data and the encounter records submitted by the public, we can get a glimpse into the life of a bird during breeding, migration, or wintering. If a bird is recaptured at another banding station or observed by the public we can collect vital information, such as sex, age, fat content, morphological measurements, seasonal and temporal differences, regional and migratory flyways patterns, among other factors, such as how it died like this bird collision. If you see a banded bird from a collision or at any other time, alive or dead, please report it using Your reports will help the USGS Bird Banding Lab track movements or the final outcomes of these birds! 

Black, gray, white and yellow small songbird being held in the hand by a bander after a USGS federal band was banded to the l
Golden-winged warbler banded on November 6, 2019, in El Jaguar Reserve, Jinotega, Nicaragua. 

Up to one billion birds are killed each year in the United States due to collisions with glass, and many birds can die during mass collision events, one of which recently occurred in Chicago when 1,000 birds struck one building, over one night.  While some collided birds are banded, many are not. This golden-winged warbler provides a small  glimpse at the huge problem of window collisions for birds.  

Dona Lili, and her husband, George Duriaux, are the operators of a “MoSI” bird monitoring station at El Jaguar Reserve where they combine habitat conservation and bird research with the production of Rainforest Alliance sustainable coffee. MoSI, named for the Spanish acronym for “Monitoring Overwinter Survival,” is a network of bird monitoring stations across the northern neotropics that monitors populations of migratory birds that depend on these areas during the non-breeding season, such as the golden-winged warbler, as well as birds that stay in the neotropics year-round.  

Established in 2002 by The Institute for Bird Populations (IBP), the MoSI program helps gather critical data across the full annual cycle of birds, helping researchers and land managers to understand what drives or limits populations, and where and when to direct conservation efforts. Stations are operated by independent banders, conservation non-profits, local universities and government agencies using a standardized mist-netting and banding protocol modeled after IBP’s Monitoring Avian Productivity and Survivorship (MAPS) program. Dona Lili and her team have been partners in the MoSI program since its inception more than 20 years ago and even hosted several of IBP’s training programs to kick off the MoSI program in 2002 and 2003.  

Sadly, this golden-winged warbler is not the first bird banded at El Jaguar Reserve to later die from a window collision. A wood thrush banded on Valentine’s Day 2011, struck a window and died in Bucks County, Pennsylvania several months later, after migrating north to nest.  



The populations of golden-winged warbler, wood thrush and many more species are rapidly declining. The golden-winged warbler has experienced over a 70% population decline in the last 50 years and the wood thrush has experienced a 60% decline. Though many factors contribute to population declines, collisions with glass are the third greatest threat to birds next to habitat loss and cats.   

A home window with white dots on it to prevent bird collisions.
Residential window with bird-safe window bird collision deterrents applied.

Birds often fail to see glass as an obstacle and collide with windows when they fly towards natural reflections of habitat, like sky or plants. Birds are also attracted to lights shining through windows or from nearby porches and yards. Although some birds may seem fine after a collision with glass, many may die later from head or other injuries. 

Fortunately, you can help change the story endings for birds like this golden-winged warbler and wood thrush by helping reduce bird collisions with windows at building where you live and work. There are simple, inexpensive, and attractive ways to help prevent bird collisions by making windows more visible to birds. To be effective, window patterns should include at least a 2-inch by 2-inch grid on the outside of windows. For low-cost, temporary methods, individuals can make and hang a paracord bird curtain or create decorative patterns using tempera paint and stencils. For more long-term solutions, individuals can consider using dense decal markers (such as dots), external, or “fritted” glass that includes exterior patterns to make the glass visible to birds). For more information on solutions, see here



Learn more: 

A Surprising Band Recovery from the USGS Bird Banding Lab’s Fall Migration Station | U.S. Geological Survey 

Don't Let the Sun Set on Evening Grosbeaks | U.S. Fish & Wildlife Service (

Bird Collisions: Current Science and Future Opportunities | U.S. Geological Survey ( 

Seven Simple Actions to Help Birds | Cornell Lab of Ornithology (


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