Monarch butterflies have officially made it to their overwintering sites in Mexico! As they continue to arrive, we’re looking back at the results from our efforts to document the migration roosting sites across Iowa.
Thank you to everyone who reported monarch roosts on their landscape! We had 16 landowners contact us about their roosts, and with additional data recorded in Journey North, we were able to document 30 roosting locations across the state! This was an excellent effort by everyone involved, and we’re excited to share with you all the summary of those efforts.
Reports of monarch roosts began to trickle in during the last week of August and continued to be reported through the first weekend of October. The size of the roosts ranged from around 10 monarchs to upwards of 500 butterflies! The average roost size was around 70 monarchs. Some landowners reported that monarchs have been using their site consistently across multiple years with one landowner noting that they’ve been seeing monarchs on their land for the past 20 years!
Monarchs used a variety of trees as their roosting site including maples, conifer trees like spruce and pine, oak trees, willows, the seven-son tree, lilac, hackberry, and mulberry. Maples were most often noted as being used by monarchs followed by conifer trees. Mulberry and seven-son trees were also reported multiple times as the choice site for resting monarchs.
Roosts were reported across all corners of the state and could be found in all sorts of land cover types including agricultural areas, grasslands, forests, and developed areas. The majority of roosts were surrounded by agricultural fields with the next most reported land cover being developed areas. This highlights the importance of providing native, fall-blooming nectar plants in these areas as it will help fuel monarchs along their journey. Trees found along the edge of forests, windbreaks, and within parks and neighborhoods are another important aspect to creating roosting habitats for monarchs across the state.
This year was our first time collecting roosting data, and we are excited to continue our efforts in the following years. Our goal is to try and find patterns of successful roosting sites and increase them across Iowa. By working with landowners across the state to create a dataset spanning multiple years, we will gain a fuller picture of where monarchs like to roost and the qualities that attract them to certain sites. Thanks again to everyone who reported data! Check back in for updates on the monarch overwintering populations as the season progresses.
Monarch Roost Photo: Liz Figanbaum