Vasectomy is simply cutting the ductus deferens which is a long tube leading from the testicle (deep within the abdomen or ‘coelom’) to the cloaca. This is the conduit for sperm to travel from the testes to the outside world. The ductus deferens is cut and a section removed preventing future inseminations. This can be done via endoscopy (mildly invasive), open coelomic surgery (most invasive) or in small songbirds (like finches) at the protrusion of the cloaca (minimally invasive). In order for vasectomy to be effective, both vas deferens must be completely transected. Depending on the species, some birds can still effectively inseminate females for up to 6 months after vasectomy. This occurs because sperm may still remain in the vas deferens segment that was not removed.
Vasectomy does not affect a bird’s behavior or plumage, just the ability to inseminate (after the tube has been completely emptied). So, this procedure is used mainly as a means of population control. Potential side effects are mostly related to surgery such as anesthetic complications (including death), cutting the wrong structure (such as the ureter and major blood vessels which lie close to the ductus deferens) and incompletely severing the ductus deferens (which may heal and still be functional).
Castration is a whole different subject. As a general statement, I do not recommend castration for anything other than testicular disease (mostly cancer). In other words, I do not recommend castration as a means of behavior modification.
A bird’s testicles are located deep within the coelom making access difficult and requiring either invasive open body or multiport endoscopic surgery. The technical difficulty of castration in large part depends on the size of the testes (which varies dramatically with breeding season and any disease present). Additionally, seemingly any remnant testicular tissue can regrow. So if a spec of testicle is left (which because of its intimate attachment to surrounding tissues is possible), it can regrow into an active, healthy and very determined organ! Caponization is castration done at a very young age before the testicle has fully developed and enlarged.
While I have castrated many birds, some regrettably for behavioral reasons, I now only consider the procedure for medical problems. My experience has been that castration for behavioral modification does not work. This includes attempting to curb aggression in parrots, ducks and poultry and crowing in poultry (chickens and peacocks). The birds temporarily stop their behaviors (probably because the surgery is invasive and they feel rotten) but have all resumed at some point later (some were even checked to make sure there was no remnant regrown testicular tissue). There are actually quite a few studies in various bird species that show the same results- once the behavior is established, castration tends to not make it stop. Some of the studies have even shown increased aggression with castrated birds. Castration would probably be most effective in preventing some behaviors (and normal adult male plumage) when done on young birds. However, I cannot justify the procedure at this time.
Part of the problem is that we are asking a bird to not perform a normal behavior such as crowing in roosters and aggressively protecting a mate (which may be a human). So I focus on understanding the behavior and look for other means of modification.
Dr Scott Echols
