Lady cardinals like their guys to be colorful. They prefer mates with the brightest red plumage because the color means he’s well fed, healthy, and has a good territory.
The cardinal’s color comes from carotenoids in the food he eats so it’s been a good breeding cue for females, but a two-year study in Ohio by OSU’s Amanda Rodewald and colleagues shows this cue is a trap in stands of Amur honeysuckle.
Amur or bush honeysuckle (Lonicera maackii) is a shrub native to Asia that was planted in North America for its beauty and to control erosion. Unfortunately it takes over rural landscapes, forming dense stands that shade out native species. It’s invasive in Pennsylvania.
Amur honeysuckle berries provide good food and carotenoids for cardinals but the shrub is a gilded trap. The OSU study found that nests built in it are more likely to be raided and those who choose to nest in it have few surviving offspring.
They found this to be true in rural landscapes but not in urban settings where bird feeders provide supplemental food and predators have a wide selection of things to eat other than cardinal babies.
Ultimately the low success of bright red males in Amur honeysuckle landscapes may cause rural cardinals to become duller red because only the dull guys have successful nests.
Just another reason to hate Amur honeysuckle.
(photo by Steve Gosser)