The breeding season of three species of kiwi (Apteryx) in captivity as determined from egg-laying dates

Records from kiwi ( Apteryx spp.) breeding centres were used to obtain laying dates of 403 North Island brown kiwi ( Apteryx australis mantelli ) eggs, 24 great spotted kiwi ( Apteryx haastii ) eggs and 25 little spotted kiwi ( Apteryx owenii ) eggs. North Island brown kiwi outdoors had an annual cycle of egg-laying with 88.5% of eggs laid from June to January. Eggs were laid in every month of the year, with fewest eggs in April (2.1 % of all eggs). The greatest number of eggs was laid in July (15.6% of all eggs), with a second peak of laying in October (13.5% of all eggs). Both the great spotted kiwi and little spotted kiwi had annual cycles of egg-laying, with the main egg-laying seasons being August-January (87.5% of eggs) for the former and July-December (96.0% of eggs) for the latter. The highest peaks of laying were in October and August, respectively. Kiwi eggs were considered to belong to the same clutch if they were laid no more than 40 days apart. Clutch size in the North Island brown and little spotted kiwi was most commonly one or two eggs. In the great spotted kiwi only clutches of one egg were found. The mean clutch size of North Island brown kiwi outdoors (1.51±0.05) did not differ from that of free-living North Island brown kiwi (1.33±0.09). Similarly, there was no difference in the mean clutch size of captive and free-living little spotted kiwi (1.39±0.14 and 1.10±0.07). The mean interval between eggs for kiwi outdoors did not differ between North Island brown kiwi and little spotted kiwi (27.4±0.5 and 30.7±1.8 days). The results indicate that all three species of kiwi maintain annual cycles of egg-laying in captivity, with the main egg-laying season being longer than in free-living birds.     

Protected areas for kiwi in mainland forests of New Zealand: how large should they be?

This paper examines, theoretically, how dispersal affects the viability of brown kiwi populations in protected areas of different size. Brown kiwi are threatened by introduced mammalian predators in mainland forests and are likely to persist only in managed forests where predators are controlled. In each protected area, the kiwi population will function as a net source, with an outflow of juveniles into the adjoining forest and minimal backflow into the reserve. Computer simulations show the minimum area of forest required for population viability increases non-linearly as the mean dispersal distance of juveniles increases. Preliminary measurements of the mean dispersal distance of brown kiwi in the wild suggest kiwi populations are unlikely to be viable in protected areas of less than 10 000 ha. Our estimate of the forest area requirement for viable populations of brown kiwi agrees with those derived by earlier workers using biogeographic techniques.     

Incubation behaviour and egg physiology of kiwi (

Incubation behaviour varies among the different taxa of kiwi. For North Island brown kiwi (Apteryx mantelli) and little spotted kiwi (A. owenii), only the male incubates the eggs, except for in the first week. Meanwhile, for Okarito brown kiwi (A. mantelli) and the tokoeka (A. australis), incubation is shared by both sexes. In addition, amongst southern tokoeka, family group members can assist with incubation to the extent that breeding males may take no part in incubation at all. This study shows that kiwi turn their eggs regularly, an observation that contradicts earlier findings. There is a mean incubation temperature of 36.5°C at the top of the egg but the bottom may be 10°C lower in North Island brown kiwi and 5-8°C lower in Okarito brown kiwi eggs. Experiments inducing water loss from fertile and infertile eggs show that the presence of an embryo does not influence rate of water loss. North Island brown kiwi, Okarito brown kiwi and tokoeka regularly have more than one clutch in a season, and some North Island brown kiwi females lay up to seven eggs each year.     

Ancient DNA Analyses Reveal Contrasting Phylogeographic Patterns amongst Kiwi (Apteryx spp.) and a Recently Extinct Lineage of Spotted Kiwi

The little spotted kiwi (Apteryx owenii) is a flightless ratite formerly found throughout New Zealand but now greatly reduced in distribution. Previous phylogeographic studies of the related brown kiwi (A. mantelli, A. rowi and A. australis), with which little spotted kiwi was once sympatric, revealed extremely high levels of genetic structuring, with mitochondrial DNA haplotypes often restricted to populations. We surveyed genetic variation throughout the present and pre-human range of little spotted kiwi by obtaining mitochondrial DNA sequences from contemporary and ancient samples. Little spotted kiwi and great spotted kiwi (A. haastii) formed a monophyletic clade sister to brown kiwi. Ancient samples of little spotted kiwi from the northern North Island, where it is now extinct, formed a lineage that was distinct from remaining little spotted kiwi and great spotted kiwi lineages, potentially indicating unrecognized taxonomic diversity. Overall, little spotted kiwi exhibited much lower levels of genetic diversity and structuring than brown kiwi, particularly through the South Island. Our results also indicate that little spotted kiwi (or at least hybrids involving this species) survived on the South Island mainland until more recently than previously thought.     

Survival of brown kiwi (

Brown kiwi (Apteryx mantelli) in central Northland have been monitored for up to 32 months of sustained exposure to brodifacoum poison. The cereal baits were placed in bait stations to target brushtail possums (Trichosurus vulpecula). Annual survival of 55 radio-tagged adult kiwi in two poisoned forest patches has been high (95.9%), and similar to that in two nearby unpoisoned forest patches and in the patches before poison was used (95.3%). The two adult birds tested of the four that died in the poisoned areas had no traces of brodifacoum at the detection limit of 0.05 mg kg(-1). With an improved detection limit of 0.02 mg kg(-1), no traces of brodifacoum were found in nine eggs collected over 18 months after adults were first exposed to the poison. Of four chicks tested (detection limit: 0.005 to 0.02 mg kg(-1)), that had apparently died of natural causes or were killed by predators, three contained traces of brodifacoum (0.01—0.18 mg kg(-1)). The median survival of 39 radio-tagged chicks in the poisoned areas (36 days) was significantly better than that of 18 chicks in untreated areas nearby (15 days). Kiwi chicks may be more vulnerable than adult kiwi to accidental poisoning because of physiological or behavioural differences; however, the effects of sustained exposure to low levels of brodifacoum poison may not be visible in the adult population for several years. At this stage of the ongoing study, the benefits to kiwi of this method of pest control outweigh the costs, because chick survival is greatly improved.     

The breeding biology and aspects of the feeding ecology of brown noddies Anous stolidus nesting near Culebra, Puerto Rico, 1985–1989

We have studied brown noddies Anous stolidus breeding on Cayo Noroeste in the Culebra National Wildlife Refuge for the past five years (1985–1989). Daily visits during our residence there each year permitted collection of precise data on arrival chronology, egg-laying and incubation patterns, egg morphometries, chick growth rates, food delivered to chicks and breeding success. Over 150 adults are now individually colour-banded, and each annual chick cohort has been uniquely marked. Some features of the breeding biology of Culebran brown noddies were similar to those reported for pairs at Atlantic and Pacific Ocean colonies; these included duration of egg development, mass of newly hatched chicks, chick growth rates and fledging periods. Other features appear unique to Culebra. These include a tightly synchronous arrival (range of first egg dates: 29 April-4 May) and short egg-laying period (about six weeks), a consistently high breeding success each year (average 84% hatching success, 88% chicks fledged from eggs hatched, 0.79 chicks fledged per pair), and an unusually narrow range of food items (two fish species) taken by adults for their own needs and those of chicks. Observations of the direction taken by adults departing the colony suggest a predictable and productive foraging area along a prominent east-west shelf-break located c. 20 km to the north. We conclude that during these five years, brown noddies on Cayo Noroeste were not limited by food during the breeding season.     

Size matters: predation risk and juvenile growth in North Island brown kiwi (

This study investigated how predation risk in North Island brown kiwi changes as the birds grow and develop. Over a 10-year period, 53 adult and 126 young kiwi were radio-tagged at Lake Waikaremoana and studied to determine survival rates, causes of death, and rates of growth. Predation loss amongst adults was low (2.49% year^-1) and caused mainly by ferrets. Young kiwi suffered intense predation from stoats during their first four months of life, but thereafter became too large (> 800 g) for stoats to kill. Juveniles took at least 880 days to attain adult size, about four times longer than expected for a 2–3 kg bird. Growth rates peaked at about the point of hatch, rather than later on in development as in other birds. We suggest that a long evolutionary history dominated by resource limitation rather than predation may account for slow rates of development in kiwi, and that differences among kiwi species in their ability to persist in the presence of stoats are explained by differences in the time that they take to reach safe-size.     

Incubation Temperatures of Great Spotted Kiwi,

Incubation temperatures of the great spotted kiwi were studied by telemetry methods at the Otorohanga Zoological Society in October 1989. The male maintained the core temperature of the egg at about 28-31.8-degrees-C. When he emerged to feed at night, the female started to incubate. She did not have a brood patch, but could heat the egg to 28-28.5-degrees-C, sufficient for embryo growth. Some of the reasons why female great spotted kiwi might help with incubation are discussed. In cold, mountain environments, the energetic costs of incubation could be so high that males alone cannot meet them. The hypothesis predicts that there are also places in the North Island where female brown kiwi (Apteryx australis mantelli) should share in incubation.     

Preference and performance of a gall-inducing sawfly: plant vigor, sex, gall traits and phenology

Four hypotheses regarding the role of predation in the population dynamics of eruptive small mammal communities were tested using the small mammal assemblage found in mixed forests in New Zealand. Large-scale (750 ha) predator removal was conducted, targeting stoats ( Mustela erminea ). House mouse ( Mus musculus ) and ship rat ( Rattus rattus ) population dynamics during an eruption were compared in areas with and without predator reduction. The success of predator reduction was measured by comparing live-capture rates of predators on treatment and non-treatment areas, and by recruitment rates of the threatened northern brown kiwi ( Apteryx australis mantelli ). Overall, predator reduction was successful, although there was a continual low rate of reinvasion. The predictions and results were that 1) Predators can slow but not prevent a population eruption. Supported: Populations of mice and rats erupted to high densities in areas with and without predator reduction, following synchronous southern beech ( Nothofagus spp.) seeding. 2) Predators cannot truncate peak prey population size. Supported: Peak densities of mice and rats were not significantly different between treatment and non-treatment areas. 3) Predators can hasten the rate of decline in prey populations during the crash phase. Not supported: There was evidence of populations of mice and rats declining slower in areas with predators removed, but none of the trends were significant. 4) Predators can limit low-phase prey populations. Equivocal: Populations of rats in beech forest, and population of mice and rats in coastline habitats were significantly higher in areas with predators removed, but were not significantly different in tawa-podocarp forest. Therefore, the role of food in driving the early stages of the mouse and rat eruption was demonstrated, but the role of predation in the decline and low phases is unclear.     

Effects of Edge Habitat and Nest Characteristics on Depredation of Artificial Nests in Fragmented Australian Tropical Rainforest

Variation in nest predation levels associated with rainforest fragmentation (edge effects) was assessed in Australia's Wet Tropics bioregion. Artificial nests were placed in the forest understorey at seven edge sites where continuous forest adjoined pasture, seven interiors (about 1 km from the edge), and six linear riparian forest remnants (50–100 m wide) that were connected to continuous forest. Four nest types were also compared, representing different combinations of two factors; height (ground, shrub) and shape (open, domed). At each site, four nests of each type, containing one quail egg and two model plasticine eggs, were interspersed about 15 m apart within a 160 m transect during September–October 2001. Predators were identified from marks on the plasticine eggs. The overall depredation rate was 66.5% of 320 nests' contents damaged over a three-day period. Large rodents, especially the rat Uromys caudimaculatus, and birds, especially the spotted catbird Ailuroedus melanotis, were the main predators. Mammals comprised 56.5% and birds 31.0% of predators, with 12.5% of unknown identity. The depredation rate did not vary among site-types, or between open and domed nests, and there were no statistically significant interactions. Nest height strongly affected depredation rates by particular types of predator; depredation rates by mammals were highest at ground nests, whereas attacks by birds were most frequent at shrub nests. These effects counterbalanced so that overall there was little net effect of nest height. Mammals accounted for 78.4% of depredated ground nests and birds for at least 47.4% of shrub nests (and possibly up to 70.1%). The main predators were species characteristic of rainforest, rather than habitat generalists, open-country or edge specialists. For birds that nest in the tropical rainforest understorey of the study region, it is unlikely that edges and linear remnants presently function as ecological population sinks due to mortality associated with increased nest predation.     

Short pulse of 1080 improves the survival of brown kiwi chicks in an area subjected to long-term stoat trapping

Many mainland populations of kiwi are declining because stoats (Mustela erminea) kill most of their chicks. Stoats are often trapped during conservation programmes, but the long-term effectiveness of trapping has not been measured. During continuous trapping of mammalian predators in the 9800?ha Whangarei Kiwi Sanctuary, the survival of brown kiwi (Apteryx mantelli) chicks declined over time. Following the use of sodium fluoroacetate (1080) to kill rats (Rattus spp.) and possums (Trichosurus vulpecula) and likely secondary poisoning of stoats, chick survival at Riponui increased from 5% to 56%, and the 62% chick survival at Rarewarewa was better than the 20% recorded in a trapped-only area nearby. We suggest that untrappable stoats accumulate in areas subjected to continuous predator trapping. Conservation managers should build into their long-term pest control programmes a periodic pulse of an alternative tool to kill pests that, for whatever reason, actively avoid the primary control tool.     

The American Avocet (Recurvirostra americana) as a paradigm for adult automimicry

Summary The body of theory concerning life-history strategies predicts that the duration of high-mortality stages should be minimized by natural selection. This is especially applicable to the avian pre-flight stage, during which growth rates typically are rapid. Using the American Avocet (Recurvirostra americana) as a paradigm, I propose a developmental strategy by which young animals can lower their mortality rates by an accelerated (and deceptive) acquisition of adult or adult-like characters. The benefit accrues when predators misidentify the vulnerable young as adults and fail to attack them because adults are much less vulnerable. This strategy, termed adult automimicry, is most likely to occur in precocial species living in open habitats.American Avocets are large, precocial, open-country shorebirds that first fly when about 4–5 weeks old. They develop a juvenal, plumage in their third week that resembles adult breeding plumage in pattern and color, even though plumage details are different. At this time chicks begin using adult foraging techniques and tend to move away rather than hide from potential predators. A few weeks later they acquire a first winter plumage that resembles adult winter plumage. Thus, avocet chicks appear unusually adult-like after their second week. This should make it difficult for distant predators to distinguish flightless chicks from volant adults.     

Cannibalism and intraguild predation of eggs within a diverse predator assemblage

Greater biodiversity among aphid predators sometimes leads to greater predator reproductive success. This could occur if cannibalism of predator eggs is consistently stronger than intraguild predation, such that diversity dilutes cannibalism risk when total predator densities remain constant across diversity levels. We compared the frequency of cannibalism versus intraguild predation by adult predators of four species [the lady beetles Coccinella septempunctata L. and Hippodamia convergens Guerin-Meneville, and the predatory bugs Geocoris bullatus (Say) and Nabis alternatus Parshley] on the eggs of three predator species (all of these predators but Nabis). For both coccinellid species, egg predation averaged across all intraguild predators was less frequent than cannibalism. In contrast, Geocoris eggs were generally more likely to be consumed by intraguild predators than by conspecifics. Closer inspection of the data revealed that Geocoris consistently consumed fewer eggs than the other species, regardless of egg species. Indeed, for lady beetle eggs it was relatively infrequent egg predation by Geocoris that brought down the average across all heterospecific predators, masking the fact that adults of the two lady beetles were no more likely to act as egg cannibals than as intraguild predators. Nabis ate eggs of the two beetles at approximately equal rates, but rarely ate Geocoris eggs. Female predators generally consumed more eggs than did males, but this did not alter any of the patterns described above. Altogether, our results suggest that species-specific differences in egg predation rates determined the relative intensity of egg intraguild-predation versus cannibalism, rather than any more general trend for egg cannibalism to always exceed intraguild predation.     

Influence of adult and egg predation on reproductive success of Epirrita autumnata (Lepidoptera: Geometridae)

We studied the effects of predation and oviposition activity on reproductive success of a late-season moth, Epirrita autumnata by exposing adult females and eggs to predation in their natural habitat in two successive years. Daily survival rates of adult females ranged from 0.4 to 0.8, average being 0.7. Most predation occurred during nights and was caused by harvestmen and other invertebrate predators. Avian predation did not have an effect on adult survival rates, most likely because of the lateness of E. autumnata flight season. Eggs were also preyed upon by invertebrate predators, although a notable proportion of egg mortality was attributable to causes other than predation. Daily survival rates of eggs were more than 0.99. Using modeling based on empirical data on eclosion of female adults, their oviposition behavior and survival rates of adults and eggs, the daily survival rates were translated into population level consequences. Adult predation was estimated to decrease reproductive success of non-outbreaking E. autumnata by 60–85 percent and egg mortality by 20–40 percent. Predation on adult lepidopterans is a mortality factor potentially as relevant as predation in any other life history stage and thus, should not be ignored in studies of population regulation.     

THE BREEDING ECOLOGY OF ROYAL TERNS STERNA (THALASSEUS) MAXIMA MAXIMA

The breeding ecology of the New World race of the Royal Tern Sterna maxima maxima was studied at colonies in Virginia and North Carolina, U.S.A., from 1967 to 1970. Colony sites are quite varied, but isolation, good distance visibility and (especially) freedom from quadruped predators seem important if not essential prerequisites. In Virginia, most adults arrive at the colony site in the last few days of March. Courtship, displaying and copulation take place at, near, and some distance from the colony site. In this the Royal Tern differs from its near relative S. sandvicensis sandvicensis which carries out these activities away from the colony site, presumably as an anti-predator device. Courtship displays are not described, but in their essentials are similar to those of other terns. Copulations continue throughout incubation and gradually disappear when the eggs hatch. No post-copulatory displays are known. Some synchrony of egg-laying is evident, but no “mass laying” occurs, the colony increasing in size steadily over a period of weeks and months. Defaecation on the nest is normal and probably serves to strengthen the nest rim against flooding by high tides. Contrary to published reports, the normal clutch is one; the largest is two, probably often from two different females. All incubating adults examined had two brood patches. Average egg measurements are 63 × 44-5 mm, and average egg weight is 64.3 g. Egg colour varies greatly, and evaluation is difficult. Eggs are probably not cryptically coloured and individual variation, as well as nest-site, are used by returning adults to identify their own eggs. Average maximum nest density is c. 7/m². Sterna sandvicensis acuflavida nests regularly, if not obligatorily, with m. maxima; interactions between the two, and possible benefits accruing to each, are discussed. Unhatched eggs were significantly nearer other nests than were successfully hatched eggs, and possible explanations are given. Incubation lasts about 30–31 days, a week longer than in most terns; both sexes incubate. Broken eggshells are never removed by the adults. Instead, after 2–3 days, the chicks leave the nest permanently to join a creche that roams freely about the immediate vicinity of the colony. Chicks remain in the creche for about 25–30 days, leaving it at fledging, approximately 30 days after hatching. While in the creche, chicks are normally fed only by their parents, who probably recognise them both vocally and visually, using the extensive variation in voice and colour of chicks characteristic of the species. Sandvicensis acuflavida chicks also are highly variable, and join Royal creches, adults of both species attending. Variation also occurs in Royals' juvenal plumage, and seems associated with extended parental care. Feeding adults normally wander up to 40 km from their colony, and this probably facilitates the intercolonial exchange of breeding birds we recorded. They feed inshore, in shallow waters, taking small fish by dives which do not go below the surface. They regularly take small soft-shell crabs in this way, and frequently water-skim like skimmers Rynchops spp., sometimes capturing food while doing so. A relationship between crab capture and water-skimming is established for the first time, and water-skimming in non-feeding contexts is mentioned. Besides the quadruped predators which they normally avoid by fleeing the colony site, Royals have no known predators beyond the egg stage. Eggs, although not chicks, are readily taken by Laughing Gulls. Relationships between the two species are discussed, emphasising their constant association the year round.     

Molecular and other biological evidence supports the recognition of at least three species of brown kiwi

The presence of morphologically crypticlineages within the threatened brown kiwi ofNew Zealand has confounded their taxonomy. Recent genetic studies (Herbert and Daugherty1994; Baker et al. 1995) revealed that atleast two phylogenetic species exist within thebrown kiwi, and suggested that further researchshould resolve the taxonomic problems. In thispaper we extend genetic analyses to includesequences from 58 brown kiwi representing fivephylogenetic lineages for four mitochondrialloci (control region, cytochrome b,ATPase 6 and ATPase 8). Major lineages ofbrown kiwi are shown to be reciprocallymonophyletic, and align with other biologicaldifferences in the ecology, behavior,morphology and parasites of kiwi. BecausemtDNA sequences of major lineages of kiwi arenot evolving in a clocklike manner, we used anew penalized likelihood method withrate-smoothing to date the divergence of NorthIsland brown kiwi and the geographicallyisolated Okarito population (rowi) at about 6.2Mya. These lineages diverged about 8.2 Myafrom the brown kiwi in Fiordland and Haast inthe southern part of the South Island, and arethus older than the species of spotted kiwi(5.8 Mya). Given their distinctness, long-termgeographical isolation, lack of hybridizationin introduced populations, and accumulation ofnew biological characters within theselineages, we hypothesize that reproductiveincompatibilities have probably arisen as well. We therefore recommend that these divergentlineages be formally recognized as fullspecies; Apteryx mantelli should bere-instated for the North Island brown kiwi,A. australis should be restricted to thetokoeka, and a new species A. rowiishould be erected to describe the rowi atOkarito. Tokoeka should be split into at leastthree conservation management units (Haast,Fiordland and Stewart Island [Rakiura]), butfurther research is required to determine theexact relationships and status of theselineages. Further investigation is alsorequired into the genetic structuring of theNorth Island brown kiwi to confirm conservationmanagement units on the North Island.     

Individual egg and chick recognition by adult royal terns (Sterna maxima maxima)

Egg-switching choice experiments involving forty-two adult royal terns in eight choice situations at Hatteras Inlet, North Carolina, revealed that incubating adults consistently recognized their own single egg when placed in a wrong but adjacent nest. Individual egg colour and marking differences probably play the major role, but features of nest site (and/or of adjacent adults) were also shown to play a significant role in recognition and settling. Only two chick-switching experiments were done, with four chicks. Three of the returning adults failed to recognize their own chicks until the latter vocalized; the fourth recognized its silent chick and called it away from the nest site. The adaptive value of individual recognition of eggs and chicks is considered for this group (Thalasseus) of densely nesting, crêche-forming terns.     

Pre- and postnatal energetics of the North Island brown kiwi (Apteryx mantelli)

In four eggs and four chicks of the North Island brown kiwi (Apteryx mantelli) we measured pre- and postnatal oxygen consumption rate (VO(2)) daily from day (d)-75 (prior to hatching) until d+25 (after hatching). The increase of embryonic VO(2) reaches a plateau phase between d-22 and d-5 (0.113 ml O(2)/g/h=59.6% of allometrically expected value of a typical 416-g egg). Mean total O(2) uptake per egg (43.01 l O(2)) corresponds to an energy turnover rate of 2.04 kJ/g during embryonic development. This is nearly identical to the expected value for all birds (2.00+/-0.8 kJ/g). Hence, the kiwi neither 'gained nor lost energy' (Calder, 1979.Biosci. 8, 461-467) by its extreme prolongation of incubation time; it is as efficient as other avian embryos. The kiwi embryo expends only approximately 17% (847 kJ) of the energy originally stored in the egg (4942 kJ). Forty-eight percent of the egg's initial yolk mass can be found as spare yolk in the hatchling and can serve as the chick's sole source of energy and substrate for tissue production for up to at least 17 days after hatching.     

THE SOCIABLE WEAVER,PART 4: PREDATORS,PARASITES AND SYMBIONTS

Maclean, G. L. 1973. The Sociable Weaver, Part 4: Predators, parasites and symbionts. Ostrich 44: 241–253.

The main nest predator of the Sociable Weaver in the Kalahari sandveld is the Cape Cobra Nala nivea. This snake causes great losses of eggs and chicks; one cobra may eat the contents of an entire nest mass at one feed. Another nest predator which causes smaller losses of eggs and chicks but great destruction to the nest masses is the Honey Badger Mellivora capensis. These are the only two nest predators on the Sociable Weaver in the study area. Predators on adult Sociable Weavers include several birds of prey and some small carnivorous mammals.

Adult Sociable Weavers have few ectoparasites and hardly any Mallophaga. A common ectoparasite on the legs of chicks is a blood-sucking Dermestes larva, which appears not to be harmful. The only endoparasite found was the nematode, Diplotriaena ozouxi, which infected the abdominal air sacs of the adults.

The nest material of the Sociable Weavers' communal nest masses was inhabited by a wealth of invertebrate animals and a few harmless reptiles such as skinks and geckos.

Some of the chambers in a Sociable Weaver nest mass may be taken over by other species of birds. Most of these, such as Redheaded Finches Amadina erythrocephala, use the chambers for breeding purposes only, but the most important avian symbiont, the Pygmy Falcon Polihierax semitorquatus, is a permanent resident in the chambers. The presence of Pygmy Falcons is resented by the weavers but the falcons may help to keep snakes away from the nest mass. Adult Sociable Weavers are not normally preyed on by Pygmy Falcons, although the falcons may occasionally take young weavers in the nest chambers.

The tops of the nest masses may be used as nest sites by the Giant Eagle Owl Bubo lacteus. Barn Owls Tyto alba may use cavities in the superstructure of nest masses for roosting in. Neither of these owls appeared to prey on the weavers.