The work, published in the journal Individual-based Ecology, set out to answer a deceptively simple question: do pigeons that move differently also carry different microbes? The feedback between host behavior and disease transmission is widely acknowledged in theory, but empirical studies demonstrating the strength and direction of the association between an individual’s pathogens, its microbiota composition and its movement remain rare. Pigeons, known reservoirs for agents such as Salmonella, Chlamydia, Cryptococcus and Escherichia, offered an ideal test case because they overlap constantly with people at urban roosts and with livestock at agricultural sites.

The team captured 308 pigeons between July 2019 and November 2021 at three dairy farms arranged along an urbanization gradient: Mevo Horon, an isolated rural settlement 13 kilometers northwest of Jerusalem; Ma’ale Hahamisha, a semi-rural kibbutz on an elevated ridge surrounded by several small settlements; and Mikve Israel, on the outskirts of the Tel Aviv metropolitan area, where 42 percent of the surrounding land is urban. Adults in good body condition above a 250-gram threshold were fitted with OrniTrack GPS transmitters in a backpack configuration, which sampled locations every ten minutes during daylight when batteries allowed. In total, 44 pigeons were tagged, and 32 accumulated 8,473 days of tracking data — an average of 265 days per individual, with some birds followed for more than two years.

Microbiome sampling relied on a combined swabbing of the choanal cleft and cloaca of every captured bird, preserving samples on paper cards for RNA extraction. From the tagged subset, 29 samples went through untargeted total RNA sequencing on a MiSeq machine — an approach the authors chose because it outperforms 16S amplicon sequencing and shotgun metagenomics by detecting viral and bacterial sequences outside the 16S locus, giving higher discriminatory power. Taxonomic profiling filtered results with strict cutoffs to limit false positives, and bacteria were analyzed primarily at the genus level, where classification accuracy is greatest. The researchers validated the sequencing results against classical colony-growth tests for Campylobacter and Salmonella, finding strong agreement between methods.

The movement data revealed a clear urban effect. Pigeons at the rural and semi-rural sites traveled roughly 2,100 to 2,500 meters per day on average, with maximum daily displacements exceeding 3,000 meters, while pigeons at the urban Mikve site covered only about 1,000 meters daily and displaced barely 1,300 meters from their roosts. The differences were statistically significant for both travel distance and displacement. The likely explanation is resource distribution: rural pigeons spent summer months foraging for grains at harvested fields far from their roosts, while urban birds foraged year-round on human waste and rarely visited distant fields. This pattern agrees with broader findings that urban animals move less thanks to stable, rich food sources.

All pigeons, regardless of site, roosted almost exclusively in buildings within human settlements and routinely visited their respective dairy farms and other anthropogenic food sources such as parks, poultry farms and commercial areas. Crucially, crossing among the three study sites was very rare, meaning each farm’s pigeon population operated largely as a closed local system — yet one that alternated constantly between urban roosts and livestock facilities, sometimes located within hundreds of meters of each other.

The microbiome results were equally striking. The top 20 most abundant bacterial genera across all sites included Escherichia, Campylobacter, Clostridium and Streptococcus — genera containing many species of disease-causing pathogens. At the species level, the researchers identified bacteria with documented illnesses in humans, cattle and poultry, confirming that the pigeons carry not just pathogen-relevant genera but pathogenic species themselves. Local studies have previously reported Salmonella and E. coli in Israeli pigeons, and the new sequencing data are consistent with that picture of substantial zoonotic potential.

Site-level differences in microbial diversity followed the urbanization gradient in an unexpected direction. Pigeons at the urban Mikve site carried significantly higher bacterial richness than those at the two rural sites, with around 160 genera per bird compared to roughly 70 at Mevo and Ma’ale Hahamisha. Fisher’s alpha diversity, a measure that accounts for evenness, showed the same trend, though it was not statistically significant across all indices. The authors caution that with only three sites, factors such as elevation, resource composition and local density cannot be ruled out, but the urbanization gradient is the obvious candidate explanation, and prior work has attributed increased microbial diversity in urban wildlife to parasite acquisition, natural infections and physiological stressors at urban habitats.

The study’s most novel finding concerns individual behavior. Among 19 pigeons with both high-quality GPS data and microbiome profiles, exploratory individuals — measured by the number of spatially unique stops they made per day — carried significantly richer and more diverse microbiota, independent of capture site. This positive association held similarly at all three sites, implying that birds visiting more diverse locations sample their region more thoroughly and encounter more bacteria along the way. An alternative mechanism cannot be excluded: the microbiome itself might shape behavior, either through sickness or through deliberate host manipulation by microbial agents. Prior work in barn owls found that individuals moving greater distances from the nest had higher microbiome alpha diversity, and gull colonies using a wider variety of foraging sites showed maximal bacterial diversity, lending independent support to the exposure hypothesis.

The combined picture — high mobility, high densities, constant proximity to humans at roosts and cattle at foraging sites, and opportunistic visits to open habitats — points to a strong potential for feral pigeons to transfer pathogens among livestock, humans and wildlife. The authors emphasize that these patterns matter in both directions: pigeons are similarly likely to transmit pathogens from poultry farms into wildlife populations, a scenario underscored by the massive 2022 avian influenza outbreak. Practically, the findings suggest disease management should be tailored to local conditions and individual variation — culling protocols in rural areas would need to operate across much larger areas than urban ones, and more exploratory pigeons should be prioritized when targeting is possible. The study offers a rare mechanistic example of the One Health premise, demonstrating how movement ecology tools can illuminate the individual-level pathways through which synanthropic species connect human, animal and environmental health.

Subject of Research: Association between movement patterns, microbiome diversity, and potential pathogens of feral pigeons in dairy farms

Article Title: Association between movement patterns, microbiome diversity, and potential pathogens of feral pigeons in dairy farms

Article References: Crafton, M. M., Lublin, A., Cahani, S., Rauer, L., & Spiegel, O. (2025). Association between movement patterns, microbiome diversity, and potential pathogens of feral pigeons in dairy farms. Individual-based Ecology, 1, Article e146376. https://doi.org/10.3897/ibe.1.146376

Image Credits: AI Generated

DOI: 10.3897/ibe.1.146376

Keywords: Association, between, movement, patterns, microbiome, diversity, potential, pathogens, feral, pigeons, dairy, farms

The question the researchers set out to answer is deceptively simple, yet it touches one of the deepest issues in visual neuroscience. In the natural world, objects rarely advertise a single identifying feature. A ripe berry is both red and round; a predator’s silhouette is both dark and shaped in a particular way. When multiple cues redundantly point to the same answer, an animal could in principle combine them all, weight them equally, or shortcut the whole computation by relying on whichever cue is easiest to extract. Humans and other mammals show complex, context-dependent weighting of such redundant cues. Whether birds — whose visual system is built along an entirely different anatomical plan — follow a similar logic, or adopt a simpler dominance rule, has remained unclear.

Earlier work had already hinted that pigeons prefer color over shape when classifying visual targets. What remained unknown was whether color merely takes the lead while shape still contributes meaningful discriminative information in the background, or whether shape is effectively sidelined once color is on the scene. Disentangling these possibilities required an experimental design in which the two types of information could be separated, combined, and compared across the same animals — and, crucially, a way to watch the brain respond as each kind of cue arrived.

The team’s approach was a transfer paradigm built around single-cue and multi-cue discriminations. Pigeons were first trained on tasks in which only one type of information was useful: some birds learned to classify images using color alone, while others had to rely on shape alone. Once these single-cue habits were firmly established, the birds were shifted to multi-cue tasks in which color and shape appeared together as redundant signals, both pointing toward the same classification response. This transition is the heart of the experiment. If a pigeon trained on color alone suddenly performs even better when shape is added, that suggests shape is being recruited as extra evidence. If performance stays flat, color was already doing the heavy lifting. Conversely, a shape-trained bird that improves when color joins the display would reveal that color carries information the bird can exploit immediately.

The behavioral results were asymmetric in a way that speaks volumes. Moving pigeons from the single-color task to the combined color-plus-shape task produced no measurable change in recognition accuracy — the birds were already performing at a level that the additional shape information could not improve. Moving them from the single-shape task to the multi-cue task, however, produced a significant boost in accuracy. The pattern indicates that color served as the primary behavioral driver of object recognition in these tasks, while shape contributed little detectable benefit once color was present. In other words, the pigeons did not behave like statisticians averaging two independent sources of evidence; they behaved like animals that had found one sufficient answer and saw little reason to look further.

What makes the study more than a behavioral curiosity is its second, neurophysiological layer. While the birds performed the tasks, the researchers recorded local field potentials — the summed electrical activity of populations of neurons — from the entopallium, the bird brain’s principal station for processing visual object information. The entopallium is the avian counterpart of structures in the mammalian visual pathway that support object recognition, making it the natural place to look for a neural signature of cue preference. If pigeons genuinely privilege color, that bias should leave traces in the strength and coordination of the entopallial response.

It did. At most of the recording sites, the local field potential responses were stronger for color cues than for shape cues, a neural asymmetry that mirrors the behavioral hierarchy. Even more intriguing was what happened to functional connectivity — the degree to which activity at different sites rises and falls together. When pigeons viewed multi-cue images, the local functional connectivity within the entopallium was less dense than when they viewed single-cue images. This counterintuitive finding suggests that when one dominant cue is sufficient, the brain may actually relax the coordinated communication that a harder, multi-feature computation would demand. Rather than integrating two streams of information and paying the neural cost of doing so, the color-dominant system appears to streamline its activity — an economy of processing that fits the idea that redundancy invites efficiency rather than elaboration.

The authors interpret this color preference as a potentially efficient strategy: when one cue is enough to classify an object accurately, relying primarily on that cue saves computational effort without sacrificing performance. There is an appealing ecological logic to this. Color in nature is often a fast, high-contrast signal — ripe versus unripe fruit, warning coloration, the flush of blood in a threat display — and a foraging or predator-avoiding bird may benefit from a visual system that locks onto such signals quickly. The new data add a mechanistic dimension to that intuition, showing that the preference is not just a habit of responding but is reflected in the raw amplitude of the brain’s visual response and in the architecture of its local communication.

The study also carries broader implications for how scientists think about avian intelligence. Birds achieve object recognition with a forebrain organization radically different from the mammalian cortex, yet they solve visual classification problems with a flexibility that sometimes rivals primates. Findings like these show that the strategies birds bring to such problems are not simply scaled-down versions of mammalian ones; they can exhibit their own characteristic biases, shaped by the statistics of natural scenes and the economics of neural processing. Understanding when and why a brain chooses to ignore redundant information — rather than exploit it — is a question that reaches beyond pigeons, informing models of attention, cue integration, and efficient coding in any visual system, including our own and those of artificial agents designed to mimic them.

Funded by the National Natural Science Funds of China, the China Postdoctoral Science Foundation, and the Science and Technology Research Project of Henan Province, the work is published open access, allowing researchers anywhere to examine the full behavioral and electrophysiological evidence. For now, the takeaway is vivid and a little humbling: the pigeon pecking at a screen in a laboratory is not weighing every scrap of information available to it. It has made up its mind about what matters — and in the world of these birds, at least under these conditions, color rules.

Subject of Research: Color-dominant visual object recognition and cue redundancy processing in pigeons

Article Title: Color-dominant processing in pigeon object recognition: behavioral and entopallial evidence from redundant-cue transfer tasks

Article References: Niu, X., Liu, R., Zhu, M., Peng, Y., Wang, Q., & Zhang, X. (2026). Color-dominant processing in pigeon object recognition: behavioral and entopallial evidence from redundant-cue transfer tasks. Animal Cognition. https://doi.org/10.1007/s10071-026-02113-w

Image Credits: AI Generated

DOI: 10.1007/s10071-026-02113-w

Keywords: pigeons, object recognition, color perception, shape perception, redundant visual cues, entopallium, local field potentials, animal cognition, visual neuroscience, cue transfer tasks, bird vision, functional connectivity

Toxoplasma gondii is an obligate intracellular protozoan that cycles between felids, its only definitive hosts, and a vast range of warm-blooded intermediate hosts, including humans. Most infections are asymptomatic, but the parasite can cause devastating disease in immunocompromised individuals and severe congenital abnormalities when acquired during pregnancy. Humans typically become infected by eating tissue cysts in undercooked meat or by ingesting sporulated oocysts shed in cat faeces that contaminate soil, water, and food. Ground-foraging birds are considered excellent sentinels of environmental contamination because they peck in soil where oocysts persist, and because infection in birds is usually subclinical, allowing viable tissue cysts to accumulate in muscle and organs over long periods.

The research team, led by Ruth Ifeoluwapo Ayoade Akinbobola of the University of Abuja, collected brain, heart, and thigh muscle from 162 free-range birds: 102 chickens, 30 pigeons, and 30 guinea fowl drawn from all six area councils of the Federal Capital Territory. Sampling ran from August 2025 to February 2026, spanning both the rainy and dry seasons. The investigators used a semi-nested polymerase chain reaction targeting the B1 gene, a multicopy locus present in roughly 35 copies per parasite genome, which yields a characteristic amplicon of about 145 base pairs in the second round of amplification. Positive samples were then Sanger-sequenced and compared with reference sequences from GenBank.

The results showed that 22 of the 162 birds carried T. gondii DNA, an overall detection rate of 13.6 percent with a 95 percent confidence interval of 9.1 to 19.7 percent. Prevalence was highest in chickens at 16.7 percent, followed by pigeons at 10.0 percent and guinea fowl at 6.7 percent, though these interspecies differences were not statistically significant. Positives were spread across the territory: chickens tested positive in all six area councils, pigeons in Kuje and Gwagwalada, and guinea fowl in Bwari and Kwali. Council-level prevalence ranged from 7.4 percent in Abaji to 22.2 percent in Kuje, a geographic spread that was also not statistically significant, suggesting that exposure to the parasite is widespread rather than clustered in particular localities.

The single strongest association with infection was seasonal. Birds sampled during the rainy season, from August to October 2025, tested positive at a rate of 24.7 percent, compared with just 2.5 percent during the dry season from November 2025 to February 2026. This tenfold difference was highly significant, and rainy-season birds had approximately 13 times higher odds of PCR positivity, with an odds ratio of 12.78. Monthly prevalence declined steadily from 31.2 percent in August to zero in December and February. The pattern fits the biology of the parasite: T. gondii oocysts survive and sporulate far better in warm, moist conditions, while the desiccating Harmattan winds and low humidity of the dry season likely curtail environmental persistence. The authors caution, however, that sampling covered only seven months, so the seasonal pattern should be confirmed across a full annual cycle.

The study also found a striking metabolic signature of infection. PCR-positive chickens weighed significantly less than their PCR-negative counterparts, with mean body weights of 1,284.8 grams versus 1,819.4 grams, a difference that was highly significant. Similar directional differences appeared in pigeons and guinea fowl, though the small number of positive birds in those species, three and two respectively, meant the comparisons were descriptive rather than statistically testable. Notably, histopathological examination of brain and liver sections from 66 birds, including all 22 PCR-positive animals, failed to reveal tissue cysts or tachyzoites under the light microscope, a reminder that focal, low-burden infections can evade histological detection and that PCR positivity reflects parasite DNA rather than confirmed viable infection.

Genetic analysis of the parasite sequences added an intriguing dimension. Three high-quality B1 gene sequences, all from chickens and deposited in GenBank under accessions PZ576184, PZ576185, and PZ576186, shared 100 percent nucleotide identity with one another across a 108-base-pair conserved core region. In a neighbour-joining phylogenetic tree, they clustered with reference sequences from Egypt, Iran, Mexico, and India, and differed by only two to four nucleotides from previously reported chicken-derived sequences from Plateau State in north-central Nigeria. The authors are careful to interpret this correctly: the B1 locus is highly conserved across T. gondii populations worldwide, so this clustering reflects sequence conservation rather than evidence of shared recent ancestry or epidemiological connectivity. Higher-resolution tools such as multilocus sequence typing or whole-genome approaches would be needed to resolve lineage structure.

The detection in guinea fowl stands out as the study’s most novel contribution. Although viable T. gondii has previously been isolated from feral guinea fowl in Brazil, and clinical outbreaks have been documented in Brazil and the United States, molecular evidence of natural infection in this species had never been reported from Africa. This matters because guinea fowl, Numida meleagris, is an indigenous African bird and a widely consumed source of animal protein across the continent. Infected birds destined for the table could contribute to foodborne transmission where meat is inadequately cooked or improperly handled, particularly given that previous Nigerian research in Benue State demonstrated haplotype sharing among T. gondii sequences from free-range chickens, pigs, and seropositive pregnant women.

The FCT chicken prevalence of 16.7 percent sits within a broader African and global context. It is lower than the 30.6 percent reported in Benue State and far below the 83.3 percent documented in Plateau State, differences the authors attribute to variation in environmental oocyst contamination, cat density, climate, husbandry practices, and methodology, including the use of the more sensitive 529-base-pair repetitive element in some earlier studies. Regionally, the FCT figure exceeds the 9.5 percent reported from Libya, matches the 13.9 percent from Ghana, and falls well below the 79.0 percent from humid highland Kenya. Globally, it aligns with a pooled molecular prevalence of 18.7 percent for birds, confirming consistency with established avian toxoplasmosis epidemiology.

The authors frame their findings within a One Health perspective, arguing that free-range poultry deserve a place in zoonotic disease surveillance programmes in the Federal Capital Territory as sentinels of environmental contamination. They also suggest that food-safety education targeting pregnant women and immunocompromised individuals could be usefully timed around the rainy season, when infection pressure appears highest. At the same time, the study is candid about its limitations: sampling sites were purposively selected, many birds were obtained from live-bird markets where rearing history was unknown, tissue pooling precluded tissue-specific detection, and the B1 target is less sensitive than the 529-base-pair element, meaning the reported prevalence may be conservative. Even so, the message is clear: the parasite that silently infects billions of people is circulating among the birds of Nigeria’s capital, and the chickens pecking in village soil may be telling public health authorities something worth hearing.

Subject of Research: Molecular detection of Toxoplasma gondii in free-range avian hosts in Nigeria

Article Title: Molecular detection and partial B1 gene sequence analysis of Toxoplasma gondii in free-range chickens, pigeons, and guinea fowl from the Federal Capital Territory, Nigeria

Article References: Akinbobola, R. I. A., Akinbobola, J. S., Ejiofor, C. E., Jolayemi, K. O., Nafarnda, W. D., & Opara, M. N. (2026). Molecular detection and partial B1 gene sequence analysis of Toxoplasma gondii in free-range chickens, pigeons, and guinea fowl from the Federal Capital Territory, Nigeria. Discover Animals, 3(1), Article 90. https://doi.org/10.1007/s44338-026-00255-2

Image Credits: AI Generated

DOI: 10.1007/s44338-026-00255-2

Keywords: Toxoplasma gondii, free-range chickens, guinea fowl, pigeons, Nigeria, B1 gene, semi-nested PCR, zoonotic disease, One Health, food safety, avian toxoplasmosis, seasonal prevalence

The research, published in The Science of Nature, took a two-pronged approach that combined living feeding trials with laboratory simulations of avian digestion. Led by Judith Burack, Eberhard Haase, Stanislav N. Gorb and Thies H. Büscher, the team selected eggs from seven phasmid species chosen specifically to represent the extraordinary morphological diversity of the order. Among them were the small capitulate eggs of Carausius morosus, the large capitulate eggs of Tirachoidea jianfenglingensis, lentil-shaped eggs of Dajaca napolovi, pinnate eggs of Phyllium mabantai, hairy eggs of Orestes draegeri, rough-surfaced eggs of Nuichua rabaeyae, and the eggs of Sungaya aeta, which females bury using a secondary ovipositor. By spanning this range of shapes, sizes and surface structures, the experimenters aimed to determine whether any egg morphology confers a survival advantage during a trip through a bird’s digestive tract.

The feeding experiments used domestic pigeons, Columba livia f. domestica, as the granivorous test subjects. For each trial, batches of 16 to 25 eggs from a single species were packed into a one-milliliter gelatin capsule that was placed deep into the bird’s throat to guarantee swallowing, sidestepping the possibility that pigeons might simply crush the eggs with their beaks. Each pigeon was then housed individually for 24 hours in a nest box fitted with a wire mesh grid above a paper sheet, allowing droppings to be collected and sieved for eggs and egg fragments. Every recovered intact egg was incubated on damp paper towels at room temperature and monitored daily for hatching. The stakes of this design were clear: any egg that survived the full digestive journey and later produced a nymph would constitute direct evidence of ornithochory, the bird-mediated dispersal conventionally associated with plants.

The results were unambiguous. Across all seven species, most eggs emerged from the pigeons ground into tiny fragments, and not a single egg that passed through the digestive system hatched afterward. The lone partial exception was Dajaca napolovi, the species with disc-shaped eggs: eight of the fifty eggs fed to pigeons were recovered structurally intact from the droppings, along with assorted eggshell pieces from other species. Interestingly, the fatty capitula of several species frequently emerged fully undamaged, a testament to the resilience of that lipid-rich structure, but capitula alone cannot hatch. The mechanical gizzard, with its grinding stones, had effectively destroyed the embryos of every species regardless of how convincingly their eggs resembled seeds. The finding echoes earlier work by Matan Shelomi, who in 2011 fed more than 900 phasmid eggs to quails and chickens and recovered only one unbroken egg.

Yet intactness alone does not guarantee viability, and this is where the study’s laboratory simulations proved decisive. The researchers dissected the digestive gauntlet into its three principal stressors: acidity, heat and mechanical abrasion. They subjected batches of 50 eggs each of Carausius morosus and Dajaca napolovi to distilled water at 38 to 42 degrees Celsius to mimic avian body temperature, to hydrochloric acid diluted to a pH of 1.9 to 2.2 matching the avian proventriculus, and to vigorous stirring with two-to-three-millimeter stones replicating gizzard action. A fourth treatment combined all three stressors, and untreated control groups allowed baseline hatching rates to be established. Eggs were then incubated for months, because phasmid embryos are famously patient, sometimes taking more than half a year to emerge.

Acidity emerged as the silent killer. In the control groups, 70 percent of Carausius morosus eggs and 72 percent of Dajaca napolovi eggs hatched, but after acid exposure the hatching rate for both species was zero. Scanning electron microscopy revealed why: the acid attacked the chorion, the outer eggshell, dissolving its mineralized layers and leaving holes, structural damage and crystalline precipitates that likely represent calcium salts leached from the shell. Phasmid eggshells are known to incorporate biomineralized material, including calcium oxalate, which lends rigidity against physical threats but turns out to be chemically vulnerable in strong acid. The findings align with prior research showing that acid exposure dissolves the calcium oxalate-rich middle layer of the chorion and degrades its mechanical properties, and with studies on mayflies and mosquitoes demonstrating that low pH disrupts embryonic development in other insects as well.

Heat and mechanical stress produced species-specific effects. For Carausius morosus, a species native to India where pre-monsoon temperatures routinely climb above 35 degrees Celsius, the heat treatment was surprisingly benign: 60 percent of heated eggs still hatched, albeit after a longer incubation of about 112 days compared to roughly 80 days in controls. Dajaca napolovi, which inhabits cooler mountainous regions of northern Vietnam, fared poorly under the same thermal challenge, with only two of 50 eggs hatching after incubation periods exceeding 200 days. Mechanical stirring with stones crushed most Carausius eggs, but a larger share of the slippery, disc-shaped Dajaca eggs survived, and ten of those hatched. Friction experiments on a motorized tilting stage explained the disparity: Dajaca napolovi eggs slid at angles as low as roughly 5 degrees on smooth substrates, compared with more than 22 degrees for Carausius morosus, meaning the Vietnamese species’ low-friction eggs may simply slip between gizzard stones rather than being crushed between them.

Synthesizing the feeding trials and the simulations, the authors conclude that successful bird-mediated dispersal of a single phasmid egg through a granivorous bird would require a trifecta of preadaptations: mechanical toughness or slipperiness to survive the gizzard, chemical resistance to withstand gastric acid, and thermal tolerance to endure body temperatures around 40 degrees Celsius. No species tested possessed all three. Even the eight structurally intact Dajaca eggs recovered from pigeon droppings failed to hatch, most likely because the acidic phase of digestion, not the mechanical phase, had already doomed their embryos. For the investigated phasmatodean species, long-distance dispersal via granivorous birds therefore appears highly unlikely, and the visual mimicry of seeds seems to serve other purposes, such as defense against egg parasites, rather than a ticket through a pigeon’s gut.

The story may not be over, however, because not all birds digest seeds the same way. Previous work by Kenji Suetsugu and colleagues showed that when eggs excised from gravid females of three phasmid species were fed to insectivorous brown-eared bulbuls, five to twenty percent remained intact depending on species, and two eggs of the flightless Japanese stick insect Ramulus mikado actually hatched. Phylogeographic analysis of Ramulus mikado has since provided evidence consistent with historical long-distance dispersal, and the facultative parthenogenesis of many phasmids means that viable eggs inside a gravid female could potentially survive her predation and be dispersed when the female herself is eaten. Because insectivorous birds lack the stone-filled gizzards of seed-eaters and process prey differently, the digestive conditions their eggs encounter may be far gentler. The Kiel team suggests that future research should examine the digestive physiology of frugivorous and insectivorous birds and the protective role of the maternal body, to determine whether rare dispersal events through predators, rather than through seed-mimicry, could explain how flightless stick insects colonize distant habitats. For now, the seed disguise remains a marvel of convergent evolution, but as a dispersal strategy aimed at granivorous birds, it appears to be a costume without a function.

Beyond the immediate question of bird digestion, the findings carry weight for a broader puzzle in phasmid biology: how flightless, slow-moving insects achieve the geographic isolation that drives speciation. With wings reduced or absent in many species and even functional wings rarely used, adult stick and leaf insects have few options for crossing inhospitable terrain. Passive transport of the egg stage has therefore long been considered the most plausible route to new habitats, making the fate of eggs inside potential animal vectors a matter of evolutionary consequence rather than mere curiosity.

The study also highlights how little is known about the chemical ecology of phasmid eggshells. The biomineralized layers that give the eggs their rigidity appear to be a double-edged adaptation, hardening the shell against physical hazards while creating a chemical vulnerability to the low pH of a bird’s proventriculus. Understanding how different species vary the composition and thickness of these layers could reveal whether any lineage has evolved genuine resistance to gastric conditions.

There is an ecological irony in the results as well. The capitulum, the lipid-rich appendage atop many phasmid eggs, chemically and visually mirrors the elaiosome of myrmecochorous seeds, and ants respond to it similarly, carrying eggs into their nests and gnawing off the capitulum without harming the embryo. Ant-mediated dispersal, unlike bird-mediated dispersal, involves no grinding gizzard and no strong acid, suggesting that the seed-mimicry of phasmid eggs may be aimed at a much smaller and far more forgiving partner than the birds the resemblance superficially invokes.

Subject of Research: Experimental testing of whether stick and leaf insect (Phasmatodea) eggs can survive digestion and dispersal by granivorous birds.

Article Title: Can granivorous birds disperse stick and leaf insect eggs? Integrating in vivo digestion trials and in vitro functional experiments

Article References: Burack, J., Haase, E., Gorb, S. N., & Büscher, T. H. (2026). Can granivorous birds disperse stick and leaf insect eggs? Integrating in vivo digestion trials and in vitro functional experiments. The Science of Nature, 113(5), Article 106. https://doi.org/10.1007/s00114-026-02157-5

Image Credits: AI Generated

DOI: 10.1007/s00114-026-02157-5

Keywords: Phasmatodea, stick insects, egg dispersal, ornithochory, granivorous birds, pigeons, seed mimicry, gizzard, gastric acid, eggshell biomineralization, friction, zoology