Careful you don't let your ducks and chickens get ahold of your fava bean plants because they will certainly eat them long before they can get tall enough to grant them some shadows to hide in during the cold, winter months. 

A great choice for tea-drinkers as there are lots of choices of tea bushes to choose from. Of course, a taller-growing variety will provide the most amount of cover for your garden flock, but since tea bushes make excellent companion plants, you have the flexibility to squeeze them into and between your fruit trees, grow them as evergreen hedges, or polka dot them throughout your permaculture food forest for added sky cover for your ducks and chickens.

More uses for the camellia sinensis tea bush in the edible landscape.

Since asparagus doesn't need to be cut back until nearly spring--when the defoliated plants are getting their leaves for the warm season-- they provide an excellent, short canopy to give your ducks or chickens some coverage from the sky. Ducks don't seem to be interested in eating the asparagus spears once they've ferned out, while they sometimes attempt to eat the seed pods which will turn red in the winter and look like brightly colored berries. They will most certainly eat the asparagus itself, which I have learned the irritating way while raising Indian Runner Ducks in the edible landscape.

Many kinds of bamboo plants are evergreen and also tall growing. Though some types of bamboo plants produce shoots that are known to be more delicious than others, bamboo shoots, in general, are edible. Bamboo plants can also provide a tall-growing canopy to block harsh winds and offer protection from harsh winter weather to your ducks or chickens. 

I've found that ducks do not try to eat bamboo shoots though they will try to pull the leaves off of the bamboo culms once they sprout. I have not witnessed my own Indian Runner Ducks actually eating these leaves. As they are very curious and bottomless pits of endless hunger, they will try to eat most anything they can reach until they decide whether or not they like it. 

Another tasty (to your ducks and chickens) choice that stays green yearround and will provide ample sky cover for the winter months. Tree collards grow to be different sizes and are another plant that can be fit in in many places given some creativity. Tree collards are also easy to propagate which you'll definitely want to do to increase the amount of forage your food forest flock has access to or to just generally grow them plenty of greens.

Lemon, orange, kumquat. If it'll survive the winter, plant it. The best part of growing citrus trees to provide a tree canopy for your garden birds is that it's one of the few things they are well-known for not eating. So, these are fruit trees that won't need to be fenced or chicken wired in once they reach a certain size. Due to the curious and incessantly nosy nature of some ducks and chickens, it is highly likely they will try to eat the flowers or fruits of your citrus trees regardless of whether they spit them out or not. So it's best to fence those in until the trees grow tall enough that the flowers and fruit can no longer be reached.