Flowers for Bats: what did we learn about nectar availability this year?

Flowers for Bats campaign

Hi USA-NPN,

This year's Flowers for Bats campaign has come to a close. Thank you for your efforts tracking flowering of cacti and agave!

Read on to find out what we learned from your observations this year. Your data are making important contributions to help the USFWS understand when and where nectar sources are available for the lesser long-nosed bat, and how these nectar sources respond to changes in the environment.

We hope that you will join us again next year. Your observations made at the same sites over multiple years are especially valuable in helping us to understand the variation in flowering in cacti and agave.

Photo: Saguaro open flowers by Arthur Yang via iNaturalist (CC-BY-NC)

What you reported on saguaro and agave this year

This year, 61 observers reported data at 47 sites - thank you for your efforts!

The map below shows your reports for open flowers in the two most reported Flowers for Bats species - Saguaro (triangles) and Palmer's century plants (square). You can explore this visualization here.

We had 17 local phenology programs report data on cacti and agave this year, along with 11 backyard observers. We appreciate our partners because they provide training for volunteers, bring in data from hard to reach locations, and participate in a variety of other conservation efforts related to the lesser long-nosed bat. Our backyard observers provide critical information about flowering timing across the urban to rural gradient.

In 2024, you captured a total of onsets of open flowers for saguaro (Carnegiea gigantea) and Palmer's century plant (Agave palmeri). Saguaros saw open flowers from May to July, and Palmer's century plant saw open flowers from June to mid-September. The gray bars represent negative observations (reporting "no" when you do not see a phenophase). This data is very important to ensuring that we aren't missing observations throughout the year, and add to our understanding of the phenology of Flowers for Bats species. You can explore these two visualizations in further on our here.

In the past six years, saguaro flowers opened in early April, peaked in May, and ended in mid-July. This year's peak in open flowers was slightly different than previous years, as the peak didn't drop as quickly as it did in other years. You can explore this visualization here.

Agave palmeri open flowers varied more between years than did saguaro. This year had a similar peak in open flowers as 2020, 2022, and 2023. In 2024, the proportion of yes records for open flowers in August was higher than average. You can explore this visualization here.

As we continue to add to this dataset, we'll continue to discover patterns of when agave and saguaro have flowers, when the peak occurs, and explore how climate variables such as temperature and precipitation influence flowering phenology.

We hope that you will join us again next year to continue reporting on your saguaros and agaves. You are helping us to learn more about when and where flowers are available for bats and other pollinators!

Nature's notebook stickers!

Would you like a holographic nature's notebook sticker (pictured at right)? Send your mailing address to samantha@usanpn.org and we will mail one to you.

Thank you for your contributions to this important project, we couldn't do it without your efforts!