Numerous predators kill hornets, including frogs, birds, lizards, bats, spiders, and hedgehogs. Some larger predators, including rats, skunks, and racoons, will occasionally attack a hornet nest in order to eat the larvae inside. These natural predators typically don’t eat enough hornets to make them an effective form of hornet control. 

Birds are often averse to certain strong scents. For instance, the odor of predator urine, such as that from foxes or hawks, can deter them. Similarly, birds may dislike the pungent aromas of garlic, onions, and chili peppers. Essential oils like peppermint, eucalyptus, and citrus can also be effective in keeping birds away. However, it's important to note that individual bird species might react differently to these scents, so it might require some experimentation to find the most effective repellent for your specific situation.

Trees that provide a habitat to bats and an abundance of bugs—their main food source—will attract bats to your yard. Because the North American landscape has changed so much in recent years, bats have a harder time finding trees with cavities to shelter in. If your yard has a dead or dying tree with a lot of sun exposure, bats will likely be drawn to it because trees with those features are less common.

Birds eat grass seed for one simple reason—it’s delicious! The seeds are rich in nutrients such as carbohydrates, proteins, and fats. Seeds are also high in energy, so humans eat trail mix loaded with seeds and nuts for long-distance activities. Grass seed, when unprotected, is also exceptionally easy to access.