If an orphaned wild bird or mammal is found, further information should be sought before attempting wildlife rehabilitation. Specialized books about hand-rearing wild and domestic mammals and birds and the National Wildlife Rehabilitators Association Web site (www.nwrawildlife.org) are valuable resources.
The following is a general overview, and all species require more information for a full course of captive care. Correct species and age identification is crucial for determination of behavioral considerations, weaning diets, and adult fate.
It is illegal to keep most species of North American wild animals as pets. Permits are required, even by veterinarians, to care for most wild species beyond initial medical care. The United States Fish and Wildlife Service and state natural resource agencies should be contacted for applicable rules.
Permanent captive placement for unreleasable wildlife may be difficult to find; thus, euthanasia should be considered when injury resolution will result in a disabled, unreleasable animal. When hand-rearing for wild release, infants should be raised with conspecifics to avoid human imprinting, using techniques that avoid habituation. Wild infants must be isolated from domestic animals to avoid becoming comfortable around them. A primary reason for wild animal admittance to wildlife rehabilitation is injury due to attack by cats or dogs.
The first step is to determine whether young are truly orphaned. If chicks are returned to nests or mammals are left alone and monitored from afar, the parent may return and resume care. Human handling does not preclude most parents accepting returned offspring. Neonatal wildlife unable to be reunited with their parents, especially unidentified species, have the best chance of survival if kept warm and taken to local wildlife rehabilitation centers. Skunks, raccoons, foxes, and bats should only be rehabilitated by professionals because of potential zoonotic diseases. Marine mammals and seabirds require specialized care facilities.
Wild neonates are often found hypothermic and dehydrated, with injuries from falls or predator attacks. All require physical examination and assessment of hydration, body temperature, and nutritional condition. Warmth, hydration, and energy are critical. Because most orphans initially cannot maintain or regulate their body temperature, supplemental heat should be provided with heating pads, hot water bottles, incandescent light bulbs, or brooders. A heat gradient for ambulatory young allows orphans to select their own comfort zone. Thermal support of immobile altricial species must be closely regulated to prevent over- or under-heating. Most birds and placental mammals have normal body temperatures warmer than that of people, and they should feel warm to the human hand.
Maintaining humidity of 50%–70% in housing reduces dehydration, and insulating orphans from direct heat prevents burns. Hypothermic orphans should be warmed until body temperature is near normal and administered warm fluids to maintain hydration or correct deficits.
Once the infant is warmed and well hydrated, the advice of a permitted rehabilitator should be obtained. Species-appropriate diets can be fed to provide energy. Infants of most species have a stomach or crop capacity of ~50 mL/kg, but initial feedings should be conservatively sized and diluted until it has been determined that the infant’s excretory systems are functioning. Overfeeding may result in regurgitation, aspiration pneumonia, or diarrhea.
Hair, feathers, skin, and eyes should be kept free of spilled food or excreta, and foods maintained hygienically. Nests/housing should be cleaned regularly and secured against vermin. Treatment for ecto- and endoparasites or fly strike may be necessary. Products deemed safe for infants of domestic species should be used, and an exotic animal formulary consulted for dosing information.
Metabolic bone disease may develop quickly in wild orphans fed inadequate diets. Corvids, other passerines, herons, egrets, shorebirds, raptors, opossums, and canids are especially susceptible, including when transitioned off formulas onto inadequately supplemented animal protein diets before skeletal maturity. Ground meat or poultry must be supplemented with calcium carbonate at 5 g/0.5 kg of meat. Growing chicks require a dietary ratio of elemental calcium:phosphorus of ~2:1 by weight. Wild neonates may be affected by infectious diseases and may pose risks to rescuers, caregivers, domestic animals, or other animals in care. Biosecurity is a must.
Birds
Nest replacements should be constructed so as to provide nonambulatory chicks with a comfortable upright posture, with the head elevated and legs folded underneath the body. Housing chicks on flat surfaces may result in splayed legs; to prevent this problem, substrates should allow for the birds' growing toes to grasp.
Nearly all North American bird species feed vertebrate or invertebrate prey to their chicks, even species that are largely herbivorous as adults. Milk and bread, hamburger, condensed milk, monkey biscuits, soaked dog food, or uncooked rice should not be fed; more appropriate diets are mentioned below by species. All species require 8–10 hours of uninterrupted sleep; do not keep chicks awake all night to be fed. Exhausted chicks often show maldigestion and crop motility problems. Unstable chicks entering care late in the day should be warmed and rehydrated, have major injuries assessed, and fed before putting them to bed for the night. Older chicks or self-feeding species require daylight-level lighting to stimulate foraging behavior. All growing chicks should gain weight every day until plateauing at or near adult weight. Chicks of some species normally exceed adult weight before weaning. Prerelease aviaries are necessary to condition all species before release. Prior to release, each bird must be athletically fit for its wild lifestyle, socially normal with conspecifics, fully capable of foraging for its normal wild diet, and have all injuries resolved.
Managing Injuries in Orphaned Birds
Fractured bones are considered life-threatening injuries to birds because of the requirement of high function for release. Trauma to soft tissues can be minimized by stabilizing fractures promptly. Elbow, carpus, spine, stifle, and hock fractures or luxations carry a poor prognosis for release, but mid-shaft long bone, clavicle, coracoid, keel, or synsacrum fractures often heal well.
Fractures of the humerus and femur heal best with a simple intramedullary pin, and pinning may be successful even in extremely young or small-bodied chicks. Minimally restrictive splints and wraps for other fractures result in fastest recovery and release. Care must be taken to not impede growth of flight feathers or bones with wraps.
Chicks should be allowed to use stabilized, fractured limbs as normally as possible during recovery to allow development of normal joints. Stable callus formation occurs in 5–7 days in nestling passerines and in 10–21 days in larger-bodied species, well before radiographic changes occur. Some species form joint contractures easily when immobilized, and all will require physical therapy during fracture healing, which must continue after a stable callus has formed for full return to function.
Chicks may heal rapidly from seemingly severe soft-tissue injuries. Lacerations should have primary closure to minimize time in captivity and reduce adverse effects on growing plumage. Antibiotic therapy against gram-negative bacteria is advisable for predator-injured chicks; it should be continued until wounds have completely healed. Meloxicam and butorphanol are commonly used for pain.
Chicks with head injuries may recover well; changes in neurologic signs can be used as prognostic indicators while giving supportive care.
Beak or jaw injuries must resolve with beak tips well aligned to ensure ability to forage normally after release.
Amputations of any part of the wings or bill render birds unreleasable. Specific toes vary in importance by species; certain toes have specific functions. Amputation of a whole foot or leg is not permitted in migratory birds, per U.S. Fish and Wildlife Service regulations.
Care of Orphaned Birds: Altricial Species
Altricial species hatch young that are nest-bound and completely dependent on parental care for days to weeks after hatch. Classically, these chicks are thought of as hatching blind, naked, and helpless, but there is taxonomic variability in whether eyes are open or closed at hatch, the amount and location of downy feathers, and whether chicks are able to pick up food or whether the parent must deliver meals into the chick's mouth directly.
These chicks should be warmed to normal body temperature, hydrated until droppings are produced, and then fed. Tiny, unfeathered chicks require environments as warm as 100°F (37.8°C); larger, feathered chicks do well initially in temperatures of 90°–95°F (32.2°–35°C). Overheated chicks may hold perpetual open-mouthed postures, droop heads over nest edges, and cease producing droppings if dehydrated.
Not all species gape/beg (eg, swifts, nightjars), and some can be very difficult to feed or uncooperative (eg, towhees). Some species stop begging when full (eg, corvids); some do not stop begging and may dangerously overeat (eg, finches, goldfinches).
Successful feeding techniques vary by species, but for many, softly whistling the bird's own begging noises while offering food helps increase cooperation during meals. This also helps redirect the seemingly inextinguishable human tendency to want to talk to the bird, which hurts the bird's ability to be released with normal wild behavior. Crops should empty between feeds, but not all species have crops (eg, insectivores, owls, piscivores). Common problems that cause lack of gaping and poor GI motility include being too cold, too hot, weak, or dehydrated; having an untreated illness or injury; and incorrect species identification, leading to incorrect expectations. Overfeeding may cause droppings that appear as undigested diet. Hatchlings require more water than older chicks.
Higher protein/fat, lower carbohydrate diets are desirable for most North American species. Puréed, high-quality kitten or ferret kibble is an acceptable temporary food for many altricial chicks, supplemented with elemental calcium at 150 mg/kg twice daily, PO, until on a more appropriate diet. Altricial chicks grow very quickly; skeletal maturation and plumage quality can be adversely impacted by feeding an inappropriate diet for more than a very short period. Puréed, skinned prey animals (quail or adult mice, including bones and organs, minus feet and heads) form an adequate diet for many species such as raptors or other carnivores. Bone fragments must be completely pulverized to avoid GI trauma. Feeder insects such as mealworms and crickets are appropriate for many as well but require vitamin and mineral supplementation to avoid nutritional deficiencies in chicks ( See table: Table 1. Vitamin and Mineral Supplementation for Songbirds and Woodpeckers Fed an All-insect Diet).
A diet of thawed-frozen prey requires vitamin supplementation as well. Vitamin E and thiamine supplementation is necessary for species ingesting frozen-thawed fish. Feeding prey frozen > 6 months should be avoided. Vitamin A may be inadequate in insect prey, and deficiency may occur if prey are fed with viscera removed. Pinky mice, insects, and small-bodied fish often contain inadequate calcium for growing birds; hence, supplementation is necessary.
Songbirds and Woodpeckers
Almost all passerines in North America feed their chicks insects and other arthropods, with portions of adult diet added as chicks mature. Vitamin- and mineral-supplemented mixed feeder insects (eg, gut-loaded mealworms, crickets, waxworms, dubia roaches, others) form an ideal diet for most species. Exceptions to this include House Finches and Goldfinches, which in the wild are fed partially digested regurgitated seeds with a small proportion of insects; these species do well on the 50/50 diet described below under Doves and Pigeons.
A simple, high-protein, hand-feeding songbird diet consists of 1 cup (116 g) kitten kibble, 1.25–1.5 cup (300–360 mL) water, 2 tbsp (14 g) powdered egg white, 750 mg calcium from CaCO3, and ½ tsp (1.4 g) powdered avian vitamins. Ingredients should not be deleted or substituted haphazardly. Kibble should be soaked and blended until smooth and then fed with an appropriately sized syringe. Hatchlings/nestlings should be fed 50 mL/kg every 20–45 minutes (by age) 12–14 hours/day (16 hours/day for insectivores). Fledglings should be hand-fed 50 mL/kg every 1–2 hours, 12 hours/day, offering an appropriate self-feeding diet. Care should be taken to not get chicks dirty with food. Feeding supplemented insects also helps keep chicks scrupulously clean. If feeding insects, chicks should be fed to satiation every 20–30 minutes, 12–16 hours/day. Chicks should be weighed every day to monitor gains and reassess if not gaining rapidly; most songbirds reach adult weight at 7–10 days of age, although this may be delayed in sick or injured chicks.
Hummingbirds
Hummingbird mothers feed their chicks nectar plus a substantial proportion of tiny arthropods such as spiders and fruit flies. A very temporary diet consists of 1 part water to 6 parts table sugar or 5% dextrose, fed every 20 minutes. Hummingbird chicks show a large, full crop on their neck that should empty between feedings. Sugar water does not meet hummingbird chick nutrient requirements because it is completely missing amino acids and fats, but complete diets are beyond the scope of this chapter. Hummingbird chicks should be transferred to an experienced caretaker immediately. Sugar water must not be spilled on the bird; feather damage and skin infections may result.
Doves and Pigeons
Dove and pigeon parents make "crop milk," which is composed of partially hydrolyzed muscle proteins and high fat with very little carbohydrate content. Parents feed crop milk exclusively for the first few days, then mix with gradually increasing proportions of adult diet until weaning chicks at about one month of age. Crop capacity is 100–120 mL/kg. Birds should be fed when crop empties, 12–14 hours/day, every 1–2 hours until eyes open and then every 3 hours until ambulating and ingesting seed. Palpating the crop before each feeding will assess self-feeding and prevent overfilling.
Raptors
Raptor hatchlings can be fed small pieces of warm, water-dipped meat every 2 hours, 12 hours/day, with blunt-tipped forceps; tiny bone pieces can be included by day 3 after hatch, and casting material (skin/hair) by day 5. The crop should empty between meals. Most species will pick up chopped prey from a dish by day 14. Feeding with a puppet parent can be done once the eyes open to reduce imprinting and habituation.
Herons and Egrets
Heron and egret parents regurgitate small fish, crustaceans, molluscs, and other prey onto the floor of the nest. Chicks are fed beak-to-beak until strong enough to pick up food on their own after about a week. In captivity, thawed-frozen fish (5–20 g, sliced diagonally if larger), live insects, crayfish, and thawed-frozen mice should be offered hourly until the chicks self-feed, then several times daily. Hatchlings may require force feeding; older chicks may eat from a dish. Using a feeding puppet reduces habituation, as does ensuring chicks grow up with conspecific companions.
Precocial Species
Precocial chicks typically are able to run and feed themselves shortly after hatching. The parent(s) broods the chicks periodically through the day and at night, providing warmth and safety. They also provide protection from predators and lead chicks to foraging areas. Once warm and secure, precocial species will drink and eat independently. Solitude stresses chicks; a mirror, small stuffed animals, clean feather duster, or chicks of closely related species can be companions. Uncommon species and debilitated hatchlings require professional rehabilitative care for a positive outcome.
Chicks that are not actively foraging during the day may be being kept too dark, too cold, or have other health problems in need of investigation. Dehydrated chicks can have blocked vents and become unable to pass droppings. Each chick's ability to produce droppings should be monitored. Debilitated hatchlings may be hypoglycemic or may require drop-by-drop oral feeding of a liquid diet every 15–30 minutes until strong enough to stand and begin eating on their own. Placing pebbles in water dishes may prevent tiny chicks such as quail or ducklings from drowning. Hatchlings require habitat brooders kept at 95°–100°F (35°–37.8°C) until older and stronger, when housing can be advanced to more elaborate naturalistic habitats, with heat lamps as needed per age and thermoregulatory ability.
Shorebirds (Killdeer, Sandpipers, Avocets)
In captivity, live, fresh-frozen, and freeze-dried small invertebrate prey (eg, tubifex worms, brine shrimp, mosquito larvae, tiny krill, small freshly shed mealworms, fly larvae, cichlid mini-pellets) should be offered in shallow water platters where chicks can step in, walk around, and forage. Fresh food should be added at least four times daily, because active chicks have voracious appetites. These species are prone to metabolic bone disease and must have adequate calcium carbonate sprinkled on all food platters. The first sign of this problem is chicks that spend excessive time sitting down rather than running around eating.
Waterfowl (Geese, Ducks, Swans)
Natural duckweed or watercress, small invertebrates, crushed hard-boiled egg, small minnows, and waterfowl starter should be offered. Access to shallow water should be controlled; chicks must be able to easily exit water to warm under a heat source. Chicks may lose waterproofing and become chilled if plumage becomes contaminated with food or droppings.
Gamebirds (Pheasants, Quail, Turkeys)
Soaked puppy kibble, small-bodied invertebrates, small clumps of grass or weeds with soil, and commercial gamebird starter can be offered. Wild gamebird chicks may be extremely stressed in captivity; quiet housing away from loud noises and observation must be ensured.
Mammals
Hypothermia and dehydration must be corrected before feeding neonatal mammals. Hairless neonates require ambient temperatures of 85°–90°F (29.4°–32.2°C), while haired infants may be housed at cooler temperatures depending on maturity and body condition. Once warm and hydrated, milk replacer should be introduced using this regimen: 100% oral electrolyte solution, gradually increasing the strength of milk replacer in one to several feedings to ¼ strength, then ½, then ¾, and finally to full strength. During this process, if the neonate develops digestive upset (vomiting, diarrhea, bloating), feeding should return to the last well-tolerated ratio. Overfeeding or sudden diet changes may cause bloating or diarrhea. Neonates need to be stimulated to eliminate by gently stroking the perineal area with warm moist gauze or tissue. Dorsal side up is normal nursing posture; infants should not be put on their backs to feed. The environment should be quiet.
Care of Orphaned Fawns
Fawns should be raised in groups with minimal human contact and kept away from dogs. Newborn to 2-day-old fawns should be fed colostrum for the first 24–48 hours. After reconstitution, one 454-g package can be administered via bottle or stomach tube over 8–10 hours (5 meals/day, 30–40 mL/kg). (See table Feeding Orphaned Fawns for all fawn feeding.
Care of Orphaned Squirrels
For squirrels, syringe-feeding is preferred. Feeding schedules for eastern gray and fox squirrel neonates should be:
birth–2 weeks old: every 2 hours
2–3 weeks old: every 3 hours (8 times/day)
4 weeks old: eliminate the late-night feed
5–6 weeks old: 5 and then 4 times/day
7–8 weeks old: 3 times/day
10 weeks old: once daily
Weight should be monitored daily, and the squirrel fed 50 mL/kg initially, gradually increasing to 70 mL/kg by 3 weeks.
Acceptable milk replacers (ratios by volume): 2:3 Fox Valley 32/40:water or 1:½:2 Esbilac®:MultiMilk®:water.
When eyes are open and squirrels are ambulatory, natural foods and rodent block can be offered; fruit should be strictly limited. Ground squirrels wean at 6 weeks old, and Western gray squirrels at 12 weeks.
Care of Orphaned Rabbits and Hares
Neonatal rabbit stomachs hold 100–125 mL/kg. Healthy neonates should be fed twice a day, although feedings up to four times a day may be needed. Use of a slip-tip syringe is preferred. If suckling response is poor, meals should be tube fed, with the volume reduced by 30% and an extra feeding to ensure adequate intake.
Acceptable milk replacers (ratios by volume): 2:1 parts KMR® powder:water (with pinch of acidophilus) or 1:1 parts Esbilac powder:water ,or 4:1:4 parts Esbilac powder:heavy cream:water.
Hares (genus Lepus) are precocial (born furred with eyes open), have an average birth weight of 110 g, and are weaned at about 7 days of age. Genus Sylvilagus (ie, eastern cottontail) young are born naked with eyes closed with an average birth weight of 30–40 g. Their eyes open at 7–10 days, and weaning occurs at 3–4 weeks. Genus Oryctolagus (European or domestic rabbit),depending on the breed, have birth weights between 30–80 g. They are more similar to Sylvilagus, with eyes open at 10 days of age and weaning taking place at 4–6 weeks.
When the eyes open, a variety of chopped leafy greens and grass (orchard, timothy, or oat) hay should be provided. Because hares are precocial ,forage should be offered immediately in addition to milk replacer. Fruits and high-sugar vegetables (eg, carrots) should be avoided.
Care of Orphaned Opossums
Infant opossums weighing < 20 g have a poor prognosis. Infants weighing 20–35 g should be fed 50 mL/kg, six times a day; those weighing 40–100 g, 50–60 mL/kg, five times a day. An acceptable milk replacer (ratio by volume) is 2:1:4 parts Esbilac , MultiMilk , and water. Tube-feeding is preferred, and a size 3.5 French red rubber catheter measured to the caudal rib may be used. If syringe feeding, a cut smoothed tomcat catheter can be attached to the syringe and the infant fed drop-wise. When eyes open (~45 g), infants can be taught to lap formula from a shallow dish. When infants weigh ~60 g and are walking, kitten kibble soaked in Esbilac can be offered. Once the infant is eating soaked kibble (~80–100 g), 10% other natural food items (crickets, worms, chopped mice, local fruits, high-calcium vegetables) can be introduced. Most opossums self-feed by the time they weigh 100–120 g. Adequate calcium intake must be ensured to prevent metabolic bone disease.
Care of Orphaned Raccoons
Gloves should always be worn when handling raccoons. Raccoons may carry rabies. Raccoons are the definitive hosts for Baylisascaris procyonis, a roundworm parasite that may be transmitted to people or other animals, primarily via feces, and may lead to fatal infection.
Newborns weigh 60–75 g, with eyes and ears sealed. Incubators are necessary until weight is > 500 g. The preferred milk replacer is KMR or Zoologic® 42/25 (1:2.25 parts powder:water). Infants should be fed via 8 French gavage tube, or drop by drop into the mouth (using a cut smoothed tomcat catheter attached to a syringe) until they are stronger and/or eyes are open. Over-feeding should be avoided. The stomach should be plump but not taut. Four PawsTM large squirrel nipple on a 6-mL syringe may be used.
Infants should be stimulated to urinate/defecate after each feed until they eliminate without stimulation. Infants should be weighed daily, and fed 50 mL/kg, six times a day, until they weigh 200 g. They can then be fed using a preemie nipple on a bottle or from a dish at the rate of 42.5 mL/kg, five times/day, until they weigh 500 g.
At a weight of 400 g, if infants are strong enough and their eyes are open, in addition to the milk replacer, “mush” made of soaked puppy chow, high-protein baby cereal, and KMR powder (with water added to create oatmeal consistency) can be offered. At 500 g, one of four feeds should be mush in a dish. At 850 g, small bits of cut fruit and soaked puppy chow should be added, decreasing milk replacer to three times a day. As the infants mature, hard puppy chow, prey items (mice, fish), egg, and 10% fruits and vegetables can be offered and formula feeds reduced.
For More Information
Duerr R.S., Gage L. (eds). Hand-rearing Birds. Wiley & Sons, 2020, 2 ed.
