Flowering Pear Trees were put on the “Do not Sell”, Invasive Species List for the Ohio Department of Agriculture last January of 2023. The problem is the fruit! When Callery Pear was sold in the United States in the 1900’s, many nurseries claimed they were sterile and would not produce fruit. Callery pears are native to Asia. The species is named for a French missionary, Joseph Callery, who first collected the tree in 1858.
As the song the 12 Days of Christmas goes, “A partridge in a pear tree”. Now the questions are “Was it nesting?” “Was it feeding?” or was it doing both. Teresa Culley (Professor, Biological Sciences, University of Cincinnati) and Nicole Hardiman published the earliest work untangling exactly what was happening with the misbehaving Callery pears They noted that European starlings would feast on the fruit.
In 2022, Olivia Clark (University of Dayton) produced a fascinating honors thesis titled, “A Starling in a Pear Tree: Assessing the Influence of Bird Dispersal on Callery Pear (Pyrus calleryana)” Likewise, she noted that European starlings are among the most common birds observed eating Calley pear fruit. She also reported that other birds will eat the fruit including American Robins (Turdus migratorius, family Turdidae) as well as Cedar Waxwings (Bombycilla cedrorum, family Bombycillidae). 
The airborne acrobatics by European starlings are known as a murmuration. It’s one of Nature’s most fascinating spectacles with thousands of starlings twisting, turning, swooping, and swirling in a synchronized close-formation aerial display. It’s a stunning example of collective animal behavior.
Although murmurations are most commonly observed in the fall, they may occasionally occur in the spring. Organized flights may arise spontaneously anytime during daylight hours; however, the most dramatic displays occur during the evening hours. However, as Clark noted in her thesis, sheer numbers point towards the intestinal tract of European starlings as being a primary distribution route for Callery pears. Research published in 2017 showed that starling murmurations could include over 30,000 individuals, thus the tremendous spread of Callery Pear seeds!!
Source: Thomas DeHaas, Buckeye Yard and Garden Line