Looking through plants, I've started noticing that all the flowers marked that they attract hummingbirds have flowers with deep, tube-like, petals. Meanwhile, it seems like the plants that are marked that they attract butterflies have clusters of tiny, star-shaped flowers.

Is this just a correlation I've noticed, or do butterflies and hummingbirds actually have a preference for the shape of flowers they visit?

Here's an example of a plant for hummingbirds:  

![Flame Honeysuckle](https://i.stack.imgur.com/Fc7S4.jpg)  

([Source](http://www.delange.org/HoneySuckleFlame/HoneySuckleFlame.htm))

Here's an example of a plant for butterflies:  

![Orange Butterfly Plant](https://i.stack.imgur.com/azick.jpg)  

([Source](http://www.gurneys.com/product/orange_butterfly_plant/perennials&sid=501681))