NASAL SALT SECRETION IN FALCONIFORM BIRDS TOM J. CADE and LEWIS GREENWALD Falconers have long known that various raptors, especially accipiters and eagles, exude a clear fluid from their nares while eating. We were reminded of this fact while handling a melanistic Gabar Goshawk (1Micronisus g&r), which we trapped in the Kalahari Desert in August 1964. As the hawk ate his prey, the small droplets of fluid that collected on our gloves had a strong salty taste. This discovery led us to look for nasal secretions in 16 species and 10 genera of Accipitridae and in eight species and three genera of Falconidae. We have studied behavioral and physiolog- ical aspects of nasal secretion in these raptors with reference to Schmidt-Nielsen’s (1964) hypothesis regarding the general necessity for birds to utilize an extrarenal mechanism of salt excretion, as an adjunct to efficient water reabsorption from the cloaca in concentrating uric acid, and also in connection with the overall water economy of carnivorous birds. MATERIALS AND METHODS We obtained birds and information from various sources. Our initial observa- tions were made on an adult male Gabar Goshawk, an adult female Red-necked Falcon (F&o chiqueru), and a pair of adult Pigmy Falcons (Polihierax semitor- quatus), which we trapped in the Kalahari Gemsbok National Park in the Republic of South Africa and subsequently transported to our laboratory at Syracuse Uni- versity. In addition, we obtained the following hawks from a bird dealer in New York: an immature Savannah Hawk (Heterospizias meridionalis) and a juvenile Yellow-headed Caracara (M&ago chimuchima), both from South America, and an immature Saker (F&o chewug) and an adult Laggar (Fake jugger) from India. Heinz Meng kindly permitted us to obtain some samples from a trained Peregrine (F&o peregrinus), Goshawk (Accipiter gent&), and Red-tailed Hawk (Buteo jamaicensis). We also made spme observations and measurements on a female American Kestrel (Falco sparverius), an immature Red-tailed Hawk, and an imma- ture Sharp-shinned Hawk (Accipiter stviatus), all from the vicinity of Syracuse, New York. Walter R. Spofford and Morlan W. Nelson made some observations for us on their captive Golden Eagles (Aquila chvysaltos), and Archie White and George Goode, taxidermists of the Transvaal Museum, and 0. P. M. Prozesky, ornithologist there, noted secretions for us in a number of captive South African eagles and hawks. We have. also been able to observe secretions at close hand in caged specimens of the Lappet-faced Vulture (Torgos trecheliotus) , Cape Vulture (Gyps copotheres) , and White-backed Vulture (Gyps africanus) at the Pretoria Zoo, and recently we have had a tame Bateleur (Terathopius ecaudatus) under close observation. Thus, our material has been drawn from four continents and represents a fairly wide taxonomic sampling of species within the Falconiformes. When a hawk expelled nasal secretions, the fluid could be collected for analysis in various ways. The simplest method was to place a sheet of aluminum foil in front of -the. bird at the level of its feet and wait for it to sneeze or sling the fluid that collected in its nares onto the foil. The droplets were immediately collected with small, volumetric pipettes ranging from 1 to 25 pl in capacity. With docile birds a 10 or 25 ~1 pipette could be inserted into one of the hawk’s nares to collect the secretion before it was voided (fig. 1). THE CONDOR, 68:338-350, 1966. 13381 NASAL SALT SECRETION IN FALCONIFORM BIRDS 339 Figure 1. Method of taking samples of nasal secretion directly from the nares of a Bateleur. Note shape of nare and the secretion that has drooled onto beak. In the normal head-up posture, the secretion drains directly down to the tomium and drips off the hooked tip of the beak. 340 TOM J. CADE AND LEWIS GREENWALD Urine samples were collected on aluminum foil sheets placed beneath the birds. If the urine had a distinct, clear, and liquid portion, this fluid was collected in a pipette in the same way the nasal secretions were taken. More often, whole urine was sucked into a small capillary tube, one end was flame sealed, and the tube wits centrifuged. The clear, liquid supernatant was used for ion analysis. Blood was obtained from a wing vein and drawn into a heparinized capillary tube. The tube was centrifuged, and the plasma supernatant was blown into a depression slide and taken up in a volumetric pipette. After any of the samples had been measured in a volumetric pipette, the contents were blown out into 2 ml of distilled water. These diluted samples were then ana- lyzed for Na+, K+, and Cat+ on a Coleman flame photometer, and for Cl- on an Aminco electric chloride titrator. Phosphate determinations were made using the method of Fiske and Subbarow ( 1925). Nasal glands were dissected from the Gabar Goshawk, the Sharp-shinned Hawk, the Red-tailed Hawk, the Savannah Hawk, the American Kestrel, one of the Pigmy Falcons, the Yellow-headed Caracara, and from a Lappet-faced Vulture collected in South West Africa and a Black Kite (J4iZva.s migrans) collected in the western Transvaal. These glands were fixed in formalin. RESULTS AND DISCUSSION The Gabar Goshawk. Micronisus gabw. This bird, which weighed 175 to 180 g, nearly always exuded a salty tasting secretion from its nares while eating and for some time after finishing a meal. Most often the fluid, which collected in the orifices of the external nares, was eliminated by vigorous head-shaking and was frequently associated with ruffling of the plumage, but sometimes this hawk also sneezed the fluid out in fine droplets. We never saw any nasal secretions except during the brief period of feeding each day, but the encrustations of salt crystals around its nares led us to believe that the bird must have secreted for some time after the meal was over. When fed a laboratory mouse, the bird secreted 10 to 15 ~1 of fluid, about half of which was voided while eating the mouse, the other half within five minutes after finishing. Fluid could be seen forming in the bird’s nares within nine minutes after it started eating. When this hawk was fed raw meat from a chicken wing, he usually did not secrete any nasal fluid at all; on a few occasions somewhat less than 2 ~1 were obtained. An intact sparrow carcass stimulated as much secretion as a mouse. Adding 0.1 g of NaCl to a mouse produced no marked change in the secretory pattern of this hawk. Salted chicken was not tried. We collected 23 nasal samples from this accipiter. The high, low, and mean values for the ionic concentrations in these samples are shown in table 1. The lowest concentrations of Na+ and Cl-, the predominant ions in the secretion, were well above the blood concentrations. The first secretion voided by the bird was usually of much higher concentration than subsequent samples; this occurred because the first secretion dissolved and mixed with crystals of salt that had accumulated in the nares from the previous day. As an example, one initial sample had a Na+ concen- tration of 2316 mmole/liter and Cl- concentration of 2441 mmole/liter. Crystals of salt were visible in the nares before the drop of fluid formed. The next secretion was less than half the concentration of the first, 1039 mmole/liter for Na+ and 770 mmole/liter for Cl-. Because of the formation of salt crystals from evaporation in the nares, it is impossible to make an unequivocal statement about the osmotic concentration of NASAL SALT SECRETION IN FALCONIFORM BIRDS 341 TABLE 1 SUMMARY OF IONIC CONCENTRATIONSIN BLOOD, URINE, AND NASAL SECRETION OF FALCONWORM BIRDS, AS MILLIMOLES PER LITER BlOCd Urine NZWIl Species Na+ K+ Ca++ Cl- Na+ K+ ca++ Cl- Nat K+ Ca++ Cl- Micronisus gabar High _--- 190 100 17 67 2316 128 56 2441 Mean 160 - - 127 73 48 6 48 1023 45 21 983 Low ---- 24 12 2 32 440 16 3 416 Number 1 1 9 9 5 5 23 18 6 20 Accipiter gentilis High - - - - 620 200 - 502 Low 130 128 - 31 380 100 - 339 Number 1 1 1 2 2 2 Buteo jamuicensis Number = 1 _--- 206 76 - 21 380 20 - 226 Heterospizias meridionalis High ---- 135 150 32 47 890 30 10 949 Mean 170 8 3123 88 123 19 43 433 16 3 455 Low ---- 40 96 6 39 255 6 1 263 Number 1 1 1 1 2 2 2 2 7 5 5 7 Terathopius ecaudatus High 100 144 - 138 520 15 - 505 Mean 45 77 - 40 259 9 - 256 Low 10 18 - 5 176 6 - 185 Number ---- 9 9- 9 10 10 - 10 Falco cherrug Number = 1 234 268 - 155 920 170 - 851 Falco peregrinus Number = 1 120 232 - 14 - - - - Falco sparverius High 190 16 - 157 340 92 6 237 - - - - Mean 187 14 5 152 103 41 4 89 - - - - Low 184 12 - 147 13 9 1 23 - - - - Number 2 2 1 2 12 10 9 12 Polihierax semitorquatus High 150 300 10 71 - - - - Mean 94 115 7 34 630 40 42 397 Low ---- 56 46 2 13 - - _ - Number 6 5 5 7 1 1 1 1 the actual secretion without cannulation of the gland. We feel, however, that the minimum values, about 450 to 500 mmole/liter for both Na+ and Cl-, approximate closely the true concentrating ability of the nasal gland in this species. There were never any definite proportions between the concentrations of the various ions; cations were always in excess. Since the amount of phosphate in the 342 TOM J.