Monarch egg

Thirteen monarch butterfly eggs were found at the Rockwood Hall section of Rockefeller State Park Preserve in Sleepy Hollow on the morning of Monday, Aug. 3. 

Led by Kimberly Castaldo, the land steward coordinator for the park, the count started at the entrance to the site, and then continued along the path to the foundation for the 204-room mansion that once occupied the property.

Rockwood Hall was the home of William Rockefeller, who co-founded the Standard Oil Company with his brother John D. Rockefeller. On July 31, a plaque was unveiled to celebrate the addition of the park to the National Register of Historic Places. 

Castaldo was joined by three student interns and six volunteers, some of whom had never seen a monarch egg, which she compared in size to half a grain of rice, with ridges. In other words, easy to miss, as pictured above.

Monarchs lay between 300 and 500 eggs, one at a time, on milkweed, of which there is an abundance at Rockwood Hall. The eggs, Castaldo explained, would likely be on the undersides of newer, tender leaves.

For almost two hours, the counters spread out among the meadows, checking leaf after leaf as the sun and the temperature rose. A few monarchs fluttered by, including one that landed on a milkweed and lingered for less than a minute.

Egg counts at Rockwood Hall were also held in June and July. In June, there were none. In July, there were 10. So far, the totals fall far below those of 2019, when the counts started. The next will be Monday, Aug. 24, from 10 a.m. to noon.

Castaldo attributes the decrease to the drier and warmer weather along the monarch’s migration route. The butterflies start in Mexico, and then head north, laying eggs along the way. As one generation dies, the next generation continues.

That remarkable migration is part of the push behind the pollinator pathway concept, which promotes the planting of native species, such as milkweed, that attract butterflies and bees. 

In the Rivertowns, the popularity of pollinator gardens continues to increase. In Dobbs Ferry, August Brosnahan, an employee of Old Croton Aqueduct State Park, planted such a garden along that trail this summer. In Ardsley, members of that community’s garden club are raising caterpillars born in their gardens.

Thanks to pollinator pathway proponents, there is more milkweed for monarchs. That positive trend needs to increase, especially as the temperature rises.

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