"The Great Crisco Debate" - The Suet vs. Lard vs. Shortening question
A question has been raised concerning the best source of fat to be used in "suet" recipes for Bluebirds. The question was raised yet again when a recipe was discovered that called for the use of lard and said "Do Not Substitute!", but didn't give any reason. Research thus far indicates that the experts do not all agree on this issue.  There is some concern that suet (raw fat from cows or sheep) goes rancid too quickly. There is also concern that pure rendered suet, (tallow), may be too high in saturated fats to be easily digested by birds. There are concerns about using vegetable shortening because of the trans fatty acids created with hydrogenation. Some concerns have also been expressed about vegetable oil having a laxative effect on birds. There is some suggestion that using a combination of rendered suet and peanut butter, lard, or vegetable oil may result in a better product for the birds' health. Here's what some of the experts and long-time Bluebirders had to say:
 

	A webpage for kids from the San Diego Zoo (now not available) gave a recipe for baking goodies for birds (all species), and suggested bacon drippings, or melted lard but says DO NOT use vegetable shortening, because it makes birds sick. No further explanation was given. However, when they were questioned about the reason for this statement, their reply was "We checked with our nutritionist and he indicates that there is no health risk associated specifically with vegetable oil (as opposed to other oils)." Note that this reply does not address shortening -- only vegetable OIL. We're awaiting further clarification.
	John Schuster of the Wild Wing Co. had this to say: "Never use Crisco. Crisco is a hydrogenated oil product with unlimited shelf life, and is not fit to eat for man or beast. To prove the point, let nature show you how eatable Crisco is by doing the Crisco test. Buy a small can of Crisco, open the can, place the exposed Crisco face up in a corner in your barn, shed, or garage, and place tasty goodies (i.e. cheese, or natural peanut butter) in a tuna fish can next to the Crisco (goodies that you know mice and rats will eat.) Over the years you will see the goodies in the tuna fish can disappear, but you will never see any evidence that something is eating the Crisco. I will sometimes use Crisco in my workshop as a cheap lubricate, but never as a food product (and that include margarine too) as I prefer butter for eating, baking, etc. It is better for you to mix beef suet (the best beef suet is found around the kidneys and your local butcher will be happy to cut it away from the kidneys for you at little to no cost) with other goodies or use the peanut butter (chunky style is best) recipes that you have seen posted. Another thing about peanut butter. Look at the labels to see if any hydrogenlage oils (remember the Crisco) are added to the peanut butter. Go with natural peanut butter only. If kept frozen, then thawed out in your refrigerator before feeding, there is no reason why you can not make loads of suet or peanut butter cake bars filled with raisins and other goodies, to be feed to your over wintering Bluebirds throughout the winter months and beyond."
	Linda Janilla Peterson, who developed the Bluebird Banquet recipe, adds this: "I did consult the bird curator at the Minnesota Zoo, and "Lakes Minnesota Macaws, Inc" [specialty bird feeding] when developing the recipe. Experts can toss out all sorts of info that support their particular opinion. We see this all the time in trials with "expert witnesses" and in politics. Even scientifically backed research is open to discussion. So most of what I say is my opinion and I have no credentials other than years of Bluebirding and birdfeeding, my career being a registered nurse. The MAIN point in any wild birdfeeding program - we are supplementing the birds diet. If we were responsible for 100% of a wild bird's diet - then in depth discussion of the nutrition we are offering would be critical. Studies using chickadees have shown that at the maximum - our offerings comprise 30% of their diet. The birds are basically using us as a fast food joint. Even when it seems that the birds are constantly at our feeders, such as during a winter storm - they are also eating their normally foraged foods at the same increase in quantity. We are supplementing their diet, or offering a short term emergency survival food. Birds in the wild will eat naturally occurring suet - it is common for all sorts of species [not just crows and vultures] to glean meat and fat from the bones & antlers of dead animals. In the wild, birds do not eat processed vegetable fats. It is also a point of controversy if humans should eat processed vegetable fats. When my daughter was small, her physician recommended avoiding ALL hydrogenated fats [that includes Crisco] - which can contribute to migraine headache suffering. The existence of health food companies/stores shows that there are controversies in human foods, too. Birds do need fat, for the various reasons . . . I have used all 3 fats sources - Crisco, lard [which is pig] and beef suet. All work in the recipe with minor adjustments to flour to keep texture right. Minor storage differences - recipes mixed with Crisco is easier to handle when refrigerated, suet can go rancid if stored too warmly. When I did selection studies as described in my article - I settled on those chosen by the birds - wild free Bluebirds. The final recipe incorporated the bird's choices in ingredients. So, enjoy feeding your birds! Be assured you are not killing them with your kind handouts! And thanks for writing. It's been quite a while since I developed the food and it's always fun to hear that people are still using it successfully."
	Bruce Burdett of the Bluebird Mailing List chimed in: "All I can tell you is that I've been feeding raw, un-treated, un-melted, un-rendered suet, straight from the meat department in the supermarket, for nigh onto 55 years now, and I've never seen any harmful effects. The birds like it, especially the various Woodpeckers, but also the Chickadees, Nuthatches, Titmice, Purple and House Finches, Bluejays, etc. Goldfinches don't go for it, and the Juncos only feed on the ground . . . I have never used Crisco, or made any kind of 'Banquet' or cake. I just cut up the raw suet and stick the chunks in the wire cage feeders. I have never used any of those factory-made cakes that come in net bags, often in the shape of bells, or something."
	Kieth Kridler of the Bluebird Mailing List also added: I don't think Crisco would actually make the Bluebirds sick but I think it  has the potential of not being digested by the Bluebirds and thus becoming a laxative. I am sure many on this list remember being forced to drink castor oil for stomach aches as it was going to slide right on through the bowels. Horses are still given doses of mineral oil to help with colic.
	Evelyn Cooper of the Louisiana Bayou Bluebird Society says: "Mine dearly love raisins. I never started out feeding mealworms, mixes or anything else, so they came to them eagerly. I added the peanut butter ball as I felt the protein helped. If I had proof that peanut butter was damaging them, I would only feed raisins and have no problem doing it. I think we need to stick as close to what nature would provide as possible as . . . they got along millions of years without our Crisco, etc. I am always one to err on the side of caution because a lot of times you can't take back the mistake. Man has already made a lot of stupid mistakes in my opinion."
	When asked by Sialis.org webmaster Bet Zimmerman about whether vegetable shortening OR vegetable oil could negatively affect a bird's digestive system if used in a suet mix, Dr. Sean Pampreen, an avian vet at the Marlborough Bird and Animal Hospital in Marlborough CT said he had never heard of vegetable oil or shortening being detrimental unless perhaps it were used in large quantities.  1 tsp. of vegetable COMBINED WITH mineral oil can be used for a bird the size of a bluejay to deal with impaction.  He noted that suet is likely to only be a supplemental food source for wild birds.  He also noted that sunflower seeds, millet and peanuts are between 45-56% oil.  He felt there would probably be no difference (from a bird health standpoint) between using suet, lard or vegetable shortening.
	Donna U. from Marlboro CT says, "I could never get any Bluebird takers for the banquet I made for three years using rendered suet (from Keith K's book's recipe) , but I had very zealous Bluebirds go after the banquet I made last year when I switched to Crisco! I had to keep making it through the nesting season this Spring because the BBs were hitting it so hard!  However, I will switch to the 0-trans fat version, which comes in brick form."
	When Bluebird Nut contacted Dr. Kirk Klasing, Professor of Avian Nutrition at the Dept. of Animal Science at UC Davis, he stated the following: "'Suet' by definition is raw fat from cattle or sheep. I would avoid it in the raw form. When suet is melted and clarified, it is called tallow. Tallow is better because it is less likely to go rancid over time. However, pure tallow is not easily digested by birds because it is high in saturated fats. Very high amounts of fatty acids are difficult to emulsify by the bile, lowering its digestibility. Adding a source of unsaturated fats, such as vegetable oil or lard, improves digestibility (80 % tallow, 20% vegetable oil or lard is a good combination - you can adjust the proportions to give the melting point desired). Peanut butter also works to increase digestibility of tallow because it is high in unsaturated fats. I do not know of evidence for a laxative effect of vegetable oil. Like tallow, vegetable shortening is solid at room temperatures. However, the hydrogenation used to make shortening results in lots of trans fatty acids. Though we don't know for sure, it is likely that the trans fatty acids are less healthy than "natural" cis fatty acids (unhydrogenated oils). In chickens, high levels of trans fatty acids deplete antioxidants in the tissues. It would be best to avoid high levels of vegetable shortening. Adding additional vitamin E and other vitamins could be useful for any "suet" cake because the primary problem with these cakes is that they go rancid over time. People who feed suet usually also feed seeds. Domestic seeds are low in most vitamins, including vitamin E. Adding a multivitamin to the suet mix could be useful. Shoot for about 25 IU of vitamin E per pound of cake. Don't use a vitamin mix that contains trace minerals, because they promote oxidation."

In conclusion, we urge you to consider the evidence, both expert and anecdotal, and draw reasonable conclusions on the use of various sources of fat in your Bluebird Suet recipes, remembering that experts frequently disagree. None of the experts indicated that a single serving or batch of any particular fat source would be harmful to a Bluebird. However, it is never a bad thing to err on the side of caution. To be absolutely safe, until more evidence is presented, it is probably best to avoid vegetable shortening if at all possible. In an emergency (hungry, begging Bluebirds, a raging blizzard, six feet of snow and an unplowed driveway, and no suet or lard in the house) you'll have to use your best judgment.