Demography and Populations

Age at First Breeding

The Eurasian Hoopoe first likely first breeds when 1-year-old (1 Cramp, S., Editor (1985). The Birds of the Western Palearctic. Volume 4. Oxford University Press, Oxford, UK. Close ).

Intervals Between Breeding

Adults appear to breed annually (1 Cramp, S., Editor (1985). The Birds of the Western Palearctic. Volume 4. Oxford University Press, Oxford, UK. Close ).

Clutch Size and Number of Clutches per Season

For clutch size, see Breeding: Eggs: Clutch Size. The number of broods, ignoring replacement clutches, varies around the world. One brood is the "norm," but two broods are somewhat common in Europe. In Switzerland, 36% (269 of 758 clutches) of females and 21% (147 of 688 clutches) of males produced a second brood (166 Hoffmann, J., E. Postma, and M. Schaub (2015). Factors influencing double brooding in Eurasian Hoopoes Upupa epops. Ibis 157(1):17–30. Close ). In southern Spain, 19% of 91 pairs laid a second clutch of eggs, including replacement clutches and attempted second broods (24 Martín-Vivaldi, M., J. J. Palomino, M. Soler, and J. J. Soler (1999). Determinants of reproductive success in the Hoopoe Upupa epops, a hole-nesting non-passerine bird with asynchronous hatching. Bird Study 46:205–216. Close ). Two broods are the norm in South Africa, but sometimes a third is laid after two successful broods (21 Skead, C. J. (1950). A study of the African Hoopoe. Ibis 92:434–463. Close ). Triple brooding is also known from Arabia (43 Jennings, M. C. (2010). Atlas of the Breeding Birds of Arabia. Fauna of Arabia 25. King Abdulaziz City for Science and Technology, Saudi Wildlife Commission & Senckenberg Forschungsinstitut und Naturmuseum, Riyadh, Saudi Arabia & Frankfurt am Main, Germany. Close ). In Switzerland, a second nesting attempt is more likely if the first occurred at an earlier date and resulted in a higher number of fledglings; females whose clutches hatched before 20 May had a >50% probability of initiating a second brood, whereas females whose first clutch hatched after 31 May rarely started a second brood (166 Hoffmann, J., E. Postma, and M. Schaub (2015). Factors influencing double brooding in Eurasian Hoopoes Upupa epops. Ibis 157(1):17–30. Close ). Additionally, older females were more likely than younger females to initiate a second brood (166 Hoffmann, J., E. Postma, and M. Schaub (2015). Factors influencing double brooding in Eurasian Hoopoes Upupa epops. Ibis 157(1):17–30. Close ).

Annual and Lifetime Reproductive Success

For the discussions that follow, "initial nesting attempt" indicates a pair's first clutch of eggs, "replacement nesting attempt" is a clutch laid after after a failed initial attempt, and "second nesting attempt" refers to a clutch laid after a successful initial attempt. Readers will note that breeding success not only varies greatly from place-to-place, but also from year-to-year at a given location. Additionally, first nesting attempts result in more fledglings/nest than do second nesting attempts.

In southern Spain, the following was noted by Martin-Vivaldi and colleagues (24 Martín-Vivaldi, M., J. J. Palomino, M. Soler, and J. J. Soler (1999). Determinants of reproductive success in the Hoopoe Upupa epops, a hole-nesting non-passerine bird with asynchronous hatching. Bird Study 46:205–216. Close ): the overall productivity among 89 pairs was 2.34 fledged young/season ± 2.24 SD, with 71% of eggs laid hatching and 47% of chicks surviving to fledge. Among initial nesting attempts, 76% of eggs hatched and 47% of hatchlings fledged, leading to 1.98 fledglings ± 1.90 SD per attempt, while among replacement nesting attempts, 40% of eggs hatched and 47% of hatchlings fledged, resulting in 0.92 fledglings ± 1.38 SD per attempt, and in second nesting attempts 67% of eggs hatched and 47% of hatchlings fledged, leading to 1.27 fledglings ± 1.71 SD per attempt. Among clutches that did survive to hatching, 27.3% had one egg that did not hatch, and 9.1% had more than one egg that did not hatch; of the 30 unhatched eggs examined, 16 did not contain an embryo. Additionally, among successful clutches, most lost at least one chick, with 67% losing more than one chick; most of the chicks found dead were younger than 10 d, and the last chick hatched was, by far, the most likely to perish.

Several studies have examined reproductive success in Switzerland. In one study, double-brooded females (n = 269) produced a mean of 9.1 fledglings/yr ± 1.9 SE, with a mean of 5.41 fledglings/yr ± 1.96 SE in their first brood and 3.69 ± 1.77 SE fledglings/year (n = 269) in their second brood, whereas 489 single-brooded females produced a mean of 4.46 fledglings/yr ± 2.10 SE; additionally, double-brooded females had a higher predicted lifetime success of 0.93 ± 0.08 recruits compared with that of single-brooded females at 0.36
± 0.03 recruits (166 Hoffmann, J., E. Postma, and M. Schaub (2015). Factors influencing double brooding in Eurasian Hoopoes Upupa epops. Ibis 157(1):17–30. Close ). In other studies, the breeding success (percent of laid eggs resulting in fledglings) varied by year: 65% in 1998, 18% in 1999, 57% in 2000, and 47% in 2001 (185 Arlettaz, R., J. Fournier, and N. Zbinden (1998). Biomonitorage de la Huppe fasciee Upupa epops en Suisse: evolution demographique a long terme (1979-1998) d'une population temoin et strategie de conservation ciblee. Rapport interne de la Station Ornithologique Suisse. Close , 186 Arlettaz, R., J. Fournier, B. Posse, A. Sierro, and N. Zbinden (2000). Conservation de la Huppe fasciee Upupa epops en Valais: suivi 1999 et premiers resultats sur I'occupation des nichoirs en batiments. Rapport interne de la Station Ornithologique Suisse. Close , 187 Arlettaz, R., A. Sierro, J. Fournier, and B. Posse (2000). Conservation de la Huppe fasciee Upupa epops en Valais: suivi 2000. Rapport interne de la Station Ornithologique Suisse. Close , 188 Schaad, M., A. Sierro, J. Fournier, B. Posse, and R. Arlettaz (2001). Conservation de la Huppe fasciee Upupa epops en Valais: suivi 2001. Rapport interne de la Station Ornithologique Suisse. Close ), with these fluctuations apparently correlated to differences in weather, especially heavy and persistent rainfall (186 Arlettaz, R., J. Fournier, B. Posse, A. Sierro, and N. Zbinden (2000). Conservation de la Huppe fasciee Upupa epops en Valais: suivi 1999 et premiers resultats sur I'occupation des nichoirs en batiments. Rapport interne de la Station Ornithologique Suisse. Close , 132 Schaad, M. (2002). Influence of weather conditions on chick provisioning activity in the Hoopoe (Upupa e. epops). Ph.D. thesis, University of Bern, Bern, Germany. Close ), and the percentage of the diet that consisted of European mole crickets (Gryllotalpa gryllotalpa), which may in turn have been related to weather (77 Fournier, J., and R. Arlettaz (2001). Food provision to nestlings in the Hoopoe Upupa epops: implications for the conservation of a small endangered population in the Swiss Alps. Ibis 143(1):2–10. Close ). In 2001, 34/43 nests fledged young, with a hatching success of 71%, and a fledging success was 73%, resulting in 139 chicks fledged (132 Schaad, M. (2002). Influence of weather conditions on chick provisioning activity in the Hoopoe (Upupa e. epops). Ph.D. thesis, University of Bern, Bern, Germany. Close ). In 2014, there were 241 nestlings in 39 broods, with 180 (74.7%) surviving until fledging (23 Hildebrandt, B., and M. Schaub (2018). The effects of hatching asynchrony on growth and mortality patterns in Eurasian Hoopoe Upupa epops nestlings. Ibis 160:145–157. Close ).

Elsewhere, in eastern Germany, first broods averaged 4.4–5.3 fledged young per nest, whereas second broods averaged 3.2–3.6 (31 Krištín, A., and G. M. Kirwan (2020). Eurasian Hoopoe (Upupa epops), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. Close ). In northeastern Slovenia, 10/13 nests were successful in fledging at least one young, with a mean of 4.2 fledged young per successful nest (123 Podletnik, M., and D. Denac (2015). Selection of foraging habitat and diet of the Hoopoe Upupa epops in the mosaic-like cultural landscape of Goričko (NE Slovenia). Acrocephalus 36:109–132. Close ). Among 21 nests in Hungary, the mean clutch size was 7.1 eggs, the mean number of hatchlings was 5.7, and the mean number of fledglings was 3.4 per nest (170 Kubik, V. (1960). Beiträge zur Fortpflanzungs − bionomie des Wiedehopfes. Zoologické Listy 9:97−110. Close ). In Punjab, Pakistan, 72% of 43 eggs laid in 6 nests hatched and 81% of the 31 chicks survived to fledging, so that 58% of eggs laid resulted in a fledged young, yielding a mean of 5.2 fledglings/nest (172 Idnan, M., H. M. Jamil, A. Javid, M. H. Abbasi, M. Altaf, A. Shahzad, and A. Naeem (2019). Studies on the Reproduction and Growth of Hoopoe (Upupa epops) in District Gujrat, Punjab, Pakistan. RADS Journal of Biological Research and Applied Science 10:102–108. Close ). In southwestern Saudi Arabia, the mean clutch size among 6 nests was 5.3 eggs, of which a mean 3.8 eggs (76%) hatched and 2.3 chicks (44%) per nest fledged (43 Jennings, M. C. (2010). Atlas of the Breeding Birds of Arabia. Fauna of Arabia 25. King Abdulaziz City for Science and Technology, Saudi Wildlife Commission & Senckenberg Forschungsinstitut und Naturmuseum, Riyadh, Saudi Arabia & Frankfurt am Main, Germany. Close ). In Israel, among three nests, two nests hatched chicks (four chicks each), with two chicks surviving to fledging in one nest and three in the other, leading to an overall yield of 1.7 fledglings/nest (133 Charter, M., Y. Leshem, A. Ezer, S. Aviel, and V. Chikatunov (2008). The first record of use of a nest box by Hoopoe Upupa epops in Israel. Acrocephalus 29:105−107. Close ).

Number of Broods Normally Reared per Season

In much of Europe, a second brood is fairly common but not the norm, and the percentage of second broods that resulted in fledged young has not been well documented, even if the mean number of young per second attempt has (1 Cramp, S., Editor (1985). The Birds of the Western Palearctic. Volume 4. Oxford University Press, Oxford, UK. Close , 24 Martín-Vivaldi, M., J. J. Palomino, M. Soler, and J. J. Soler (1999). Determinants of reproductive success in the Hoopoe Upupa epops, a hole-nesting non-passerine bird with asynchronous hatching. Bird Study 46:205–216. Close , 166 Hoffmann, J., E. Postma, and M. Schaub (2015). Factors influencing double brooding in Eurasian Hoopoes Upupa epops. Ibis 157(1):17–30. Close , 31 Krištín, A., and G. M. Kirwan (2020). Eurasian Hoopoe (Upupa epops), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. Close ). In South Africa, most birds appear to raise two broods and sometimes are successful in raising three (21 Skead, C. J. (1950). A study of the African Hoopoe. Ibis 92:434–463. Close ).

Proportion of Total Females that Rear ≥ One Brood to Nest-Leaving

Information needed.

The estimated lifespan is 4–6 years for birds breeding in Germany (5 Glutz von Blotzheim, U. N., and K. M. Bauer (1980). Handbuch der Vögel Mitteleuropas. Band 9 Columbiformes-Piciformes. Akademische Verlagsgesellschaft, Wiesbaden, Germany. Close ). In Switzerland, the model-averaged apparent survival was nearly identical for males and females, and perhaps unexpectedly, those adults with greater reproductive success had a higher survival rate than those with poorer reproductive success: the probability of survival among birds with no breeding success, medium breeding success, and high breeding success was estimated at 20%, 42%, and 58%, respectively (85 Bötsch, Y., R. Arlettaz, and M. Schaub (2012). Breeding dispersal of Eurasian Hoopoes (Upupa epops) within and between years in relation to reproductive success, sex, and age. Auk 129(2):283−295. Close ). In a second study from Switzerland, the mean annual survival rate of adults, taken as a whole, was measured at 38.4% and that of juveniles was 12.1% (based on the number of juveniles returning to their natal area), but the actual juvenile survival rate was thought to be closer to 20%, with the difference due to the emigration of some juveniles to other populations (158 Schaub, M., T. S. Reichlin, F. Abadi, M. Kéry, L. Jenni, and R. Arlettaz (2012). The demographic drivers of local population dynamics in two rare migratory birds. Oecologia 168:97–108. Close ).

Body Parasites

The feather louse, Upupicola upupae, was found on 40% of 30 Eurasian Hoopoe in Uttar Pradesh, India (with no other phthirapteran species were found); the adult Upupicola upupae inhabited the wings and crest feathers, the nymphs were mostly on the basal portion of the neck feathers, while most of the eggs occurred on the wings and crest feathers (189 Agarwal, G. P., A. Ahmad, A. Rashmi, G. Arya, N. Bansal, and A. K. Saxena (2011). Bio-ecology of the louse, Upupicola upupae, infesting the Common Hoopoe, Upupa epops. Journal of Insect Science 11:46. Close ). This same species was found on 77–85% of birds on the Balearic Islands during August and September, infesting only the crown feathers, and there found mostly on the dark portions of the feather, thus somewhat camouflaging this dark species of louse (190 Mester, H. (1977). Incidence of Upupicola upupae in the crest of the hoopoe. Angew Parasitology 18:215–219. Close ).

The nematode Sicarius hoopoe is known only to occur in the Eurasian Hoopoe, was first described in Bareilly, India in 1972, and can cause ulcerations in the ventriculus or gizzard (191 Sharma, R. K. (1972). A new nematode Sicarius hoopoe n.sp. (Habronematinae) from a bird. Zoologischer Anzeiger 187:303–306. Close ). One of ten Eurasian Hoopoe examined in Egypt bore ticks, which were of the species Hyalomma marginatum rufipes (192 Hoogstraal, H., M. A. Traylor, S. Gaber, G. Malakatis, E. Guindy, and I. Helmy (1964). Ticks (Ixodidae) on Migrating Birds in Egypt, Spring and Fall 1962. Bulletin of the World Health Organization 30:355–367. Close ). Larvae of the fly, Carnus hemapterus, have been found in Eurasian Hoopoe nests; these are hematophagous nest ectoparasites that negatively affect hatchling growth but, not, apparently breeding success (193 Mazorra-Alonso, M., M., Martín-Vivaldi, J. M. Peralta-Sánchez, and J. J. Soler (2020). Autoclaving nest-material remains influences the probability of ectoparasitism of nestling hoopoes (Upupa epops). Biology 10:306. Close ).

Nest Failure

In southern Spain, 40% of nests failed, with 55% of failures due to predation (about 2:1 predation of chicks:eggs), 17% of failures due to the female dying in the nest (for unknown reasons, but not predation), 17% due to nest abandonment, 4% due to chick starvation, and 7% due to "other" causes, which included nest flooding and, likely, exposure (24 Martín-Vivaldi, M., J. J. Palomino, M. Soler, and J. J. Soler (1999). Determinants of reproductive success in the Hoopoe Upupa epops, a hole-nesting non-passerine bird with asynchronous hatching. Bird Study 46:205–216. Close ). In Switzerland, heavy rain over several days lead to increased nest failure and abandonment; in some cases, nests that were abandoned still had living chicks, and when several broods of abandoned chicks were brought into captivity, they grew normally but exhibited neurodevelopmental abnormalities (132 Schaad, M. (2002). Influence of weather conditions on chick provisioning activity in the Hoopoe (Upupa e. epops). Ph.D. thesis, University of Bern, Bern, Germany. Close ). Infanticide has been recorded in India (194 Bomford, T. (1908). A Hoopoe incident. Journal of the Bombay Natural History Society 18(4):904–905. Close ), presumably by a replacement male (195 Ghosh, S. (1999). Infanticide in Hoopoe Upupa epops Linnaeus. Journal of the Bombay Natural History Society 96(2):318–319. Close ).

Adult Mortality

Information needed.

Individual Distance

Little information. In areas where nesting heavily dependent on nestboxes, the distance between nests would be somewhat influenced by nestbox placement. In Israel, active nests can be within 70 m of each other (75 Shirihai, H. (1996). The Birds of Israel: A Complete Avifauna and Bird Atlas of Israel. Academic Press, London, UK. Close ), and in southwestern Saudi Arabia, they can be within 150 m of each other (43 Jennings, M. C. (2010). Atlas of the Breeding Birds of Arabia. Fauna of Arabia 25. King Abdulaziz City for Science and Technology, Saudi Wildlife Commission & Senckenberg Forschungsinstitut und Naturmuseum, Riyadh, Saudi Arabia & Frankfurt am Main, Germany. Close ).

Home Range and Territory Size

In Europe, Eurasian Hoopoe males defend their nest site but not their home range (122 Barbaro, L., L. Couzi, V. Bretagnolle, J. Nezan, and F. Vetillard (2008). Multi-scale habitat selection and foraging ecology of the Eurasian Hoopoe (Upupa epops) in pine plantations. Biodiversity and Conservation 17:1073–1087. Close , 85 Bötsch, Y., R. Arlettaz, and M. Schaub (2012). Breeding dispersal of Eurasian Hoopoes (Upupa epops) within and between years in relation to reproductive success, sex, and age. Auk 129(2):283−295. Close ), but in South Africa, males often defend feeding areas within their home range as well as the nest site itself (21 Skead, C. J. (1950). A study of the African Hoopoe. Ibis 92:434–463. Close ). The size of a home range likely varies with prey abundance, the distribution and number of feeding locations, and the distance from the nest to feeding sites. In northeastern Slovenia, the mean home range varied from 7.3–57.7 ha, within which the percentage of foraging habitat did not exceed 18% (123 Podletnik, M., and D. Denac (2015). Selection of foraging habitat and diet of the Hoopoe Upupa epops in the mosaic-like cultural landscape of Goričko (NE Slovenia). Acrocephalus 36:109–132. Close ). In the maritime pine plantations (Pinus pinaster) of southwestern France, the mean home range was 12.78 ha ± 5.96 SD, range 7.41–30.76 (122 Barbaro, L., L. Couzi, V. Bretagnolle, J. Nezan, and F. Vetillard (2008). Multi-scale habitat selection and foraging ecology of the Eurasian Hoopoe (Upupa epops) in pine plantations. Biodiversity and Conservation 17:1073–1087. Close ). In Israel, home ranges varied from 20–70 ha (75 Shirihai, H. (1996). The Birds of Israel: A Complete Avifauna and Bird Atlas of Israel. Academic Press, London, UK. Close ). The average radius of home ranges in Switzerland was 355 m (196 Tagmann-Ioset, A., M. Schaub, T. S. Reichlin, N. Weisshaupt, and R. Arlettaz (2012). Bare ground as a crucial habitat feature for a rare terrestrially foraging farmland bird. Acta Oecologia 39:25–32. Close ).

Breeding Density

In western Spain, the typical density is 2.1–2.5 pairs/100 ha but can reach 12–14 pairs/100 ha (197 Rehsteiner, U. (1996). Siedlungsdichte und Habitatanspruche des Wiedehopfes Upupa epops in Extremadura (Spanien). Ornithologische Beobachter 93(3):277–287. Close ). In southwestern France, the density ranged from 2.2–5.0 pairs/100 ha (122 Barbaro, L., L. Couzi, V. Bretagnolle, J. Nezan, and F. Vetillard (2008). Multi-scale habitat selection and foraging ecology of the Eurasian Hoopoe (Upupa epops) in pine plantations. Biodiversity and Conservation 17:1073–1087. Close ).

Numbers

The global population is estimated at 5,000,000–10,000,000 individuals (198 Krištín, A. and G. M. Kirwan (2015). Common Hoopoe (Upupa epops). In Handbook of the Birds of the World Alive (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors), Lynx Edicions, Barcelona, Spain. Close ). The European population is estimated at 1,300,000–2,760,000 pairs, which equates to 2,600,000–5,530,000 mature individuals (199 BirdLife International (2015). European Red List of Birds. Office for Official Publications of the European Communities, Luxembourg. Close ). Other population estimates are few. The population in Iberia is ca. 600,000 pairs, European Russia 158,000 pairs, and France 30,000 pairs (31 Krištín, A., and G. M. Kirwan (2020). Eurasian Hoopoe (Upupa epops), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. Close ). The population in Hungary is estimated at 13,500–17,500 pairs (200 Halmos, G., K. Nagy, Z. Karcza, and T. Szep (2015). The status of Hoopoe (Upupa epops) in Hungary: A review. Ornis Hungarica 23:1–9. Close ), and the Arabian population is estimated at 46,000 pairs, of which 500–1,000 are in the United Arab Emirates (43 Jennings, M. C. (2010). Atlas of the Breeding Birds of Arabia. Fauna of Arabia 25. King Abdulaziz City for Science and Technology, Saudi Wildlife Commission & Senckenberg Forschungsinstitut und Naturmuseum, Riyadh, Saudi Arabia & Frankfurt am Main, Germany. Close , 201 Pedersen T., S. J. Aspinall, O. J. Campbell, and M. C. Smiles (2021). EBRC Annotated Checklist of the Birds of the United Arab Emirates. Emirates Bird Records Committee Close ). The population in Israel stood at 5,000–10,000 pairs in the early 1990s (75 Shirihai, H. (1996). The Birds of Israel: A Complete Avifauna and Bird Atlas of Israel. Academic Press, London, UK. Close ). More information is needed regarding African and Asian populations.

Trends

Overall, populations in Europe are declining, especially in peripheral populations, a trend that has been apparent since the late 1800s and early 1900s (31 Krištín, A., and G. M. Kirwan (2020). Eurasian Hoopoe (Upupa epops), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. Close ), though nestbox programs have led to a reversal of this trend in Switzerland (158 Schaub, M., T. S. Reichlin, F. Abadi, M. Kéry, L. Jenni, and R. Arlettaz (2012). The demographic drivers of local population dynamics in two rare migratory birds. Oecologia 168:97–108. Close ) and Germany (202 Gedeon, K., C. Grüneberg, A. Mitschke, C. Sudfeldt, W. Eikhorst, S. Fischer, M. Flade, S. Frick, I. Geiersberger, B. Koop, M. Kramer, T. Krüger, N. Roth, T. Ryslavy, S. Stübing, S. R. Sudmann, S. Steffens, F. Vökler, and K. Witt (2014). Atlas Deutscher Brutvogelarten [Atlas of German Breeding Birds]. Stiftung Vogelmonitoring Deutschland und Dachverband Deutscher Avifaunisten, Münster, Germany. Close ). Few specific data are available, but in Hungary the population declined at 1.3% ± 2.5% SE annually from 1999–2014 (200 Halmos, G., K. Nagy, Z. Karcza, and T. Szep (2015). The status of Hoopoe (Upupa epops) in Hungary: A review. Ornis Hungarica 23:1–9. Close ). In both Israel and Arabia, agriculture has increased the range and population of the Eurasian Hoopoe (75 Shirihai, H. (1996). The Birds of Israel: A Complete Avifauna and Bird Atlas of Israel. Academic Press, London, UK. Close , 43 Jennings, M. C. (2010). Atlas of the Breeding Birds of Arabia. Fauna of Arabia 25. King Abdulaziz City for Science and Technology, Saudi Wildlife Commission & Senckenberg Forschungsinstitut und Naturmuseum, Riyadh, Saudi Arabia & Frankfurt am Main, Germany. Close ), though some of that gain in Israel is being reversed by the introduction of the Rose-ringed Parakeet (Psittacula krameri), which competes with the Eurasian Hoopoe for nest holes (203 Yosef, R., P. Zduniak, and M. Zmihorski (2016). Invasive ring-necked parakeet negatively affects indigenous Eurasian hoopoe. Annales Zoologici Fennici 53:281–287. Close ). The Rose-ringed Parakeet was first found nesting in southern Israel in 2002 in a date (Phoenix dactylifera) grove; subsequently, the breeding density of the Eurasian Hoopoe dropped from ca. 1.8 pairs/ha to nearly zero from 2001–2009 at one date grove and from 1.2 to 0.4 birds/ha at another (203 Yosef, R., P. Zduniak, and M. Zmihorski (2016). Invasive ring-necked parakeet negatively affects indigenous Eurasian hoopoe. Annales Zoologici Fennici 53:281–287. Close ).

There are two main factors that influence the population of the Eurasian Hoopoe — availability of both nest holes and high quality prey (24 Martín-Vivaldi, M., J. J. Palomino, M. Soler, and J. J. Soler (1999). Determinants of reproductive success in the Hoopoe Upupa epops, a hole-nesting non-passerine bird with asynchronous hatching. Bird Study 46:205–216. Close , 204 Arlettaz, R., J. Fournier, and N. Zbinden (2000). Évolution démographique (1979-1998) d’une population témoin de Huppe fasciée Upupa epops en Valais et stratégie de conversation ciblée. Nos Oiseaux 47(1):19–27. Close ). The importance of prey availability is further stressed in that Eurasian Hoopoe chicks reach their maximum mass (which is approximately 20% greater than that of an adult) and then lose weight just before fledging (24 Martín-Vivaldi, M., J. J. Palomino, M. Soler, and J. J. Soler (1999). Determinants of reproductive success in the Hoopoe Upupa epops, a hole-nesting non-passerine bird with asynchronous hatching. Bird Study 46:205–216. Close ), a pattern typical of passerines with unstable food resources or unstable access to food resources (205 O'Connor, R. J. (1978). Growth strategies in nestling passerines. Living Bird 16:209–238. Close ).

In Europe (Upupa epops epops), clutches are typically greater than the number of nestlings that might be expected to fledge most years (24 Martín-Vivaldi, M., J. J. Palomino, M. Soler, and J. J. Soler (1999). Determinants of reproductive success in the Hoopoe Upupa epops, a hole-nesting non-passerine bird with asynchronous hatching. Bird Study 46:205–216. Close , 186 Arlettaz, R., J. Fournier, B. Posse, A. Sierro, and N. Zbinden (2000). Conservation de la Huppe fasciee Upupa epops en Valais: suivi 1999 et premiers resultats sur I'occupation des nichoirs en batiments. Rapport interne de la Station Ornithologique Suisse. Close , 132 Schaad, M. (2002). Influence of weather conditions on chick provisioning activity in the Hoopoe (Upupa e. epops). Ph.D. thesis, University of Bern, Bern, Germany. Close ), an approach that has been labelled "optimistic" (206 Mock, D. W., and L. S. Forbes (1995). The evolution of parental optimism. Trends in Ecology and Evolution 10:130–134. Close ), and their eggs hatch asynchronously (see Breeding: Eggs). Parental optimism is common among asynchronously hatching bird species (207 Lack, D. (1947). The significance of clutch size. Ibis 89:302-352. Close , 208 Lack, D. (1954). The Natural Regulation of Animal Numbers. Oxford University Press, London, United Kingdom. Close ), as both would likely benefit species that face uncertain food supplies, as is explained by the brood reduction hypothesis (or some of its variants, such as the hypothesis of ensuring chick quality; 207 Lack, D. (1947). The significance of clutch size. Ibis 89:302-352. Close , 209 Amundsen, T., and T. Slagsvold (1996). Lack's brood reduction hypothesis and avian hatching asynchrony: what's next? Oikos 76:613–620. Close ). As the brood reduction hypothesis would predict, Eurasian Hoopoe chicks gain weight independent of hatching order in high quality territories, whereas the weight gain of early-hatched chicks was distinctly superior to that of late-hatched chicks in poor quality territories (23 Hildebrandt, B., and M. Schaub (2018). The effects of hatching asynchrony on growth and mortality patterns in Eurasian Hoopoe Upupa epops nestlings. Ibis 160:145–157. Close ). Notably, in South Africa, Upupa epops africana females lay smaller clutches which hatch synchronously (21 Skead, C. J. (1950). A study of the African Hoopoe. Ibis 92:434–463. Close ), suggesting that prey supplies are more stable, and perhaps, prey may have less of an influence on population numbers.