Elf Owl
(Micrathene whitneyi)
- DESCRIPTION
- DISTRIBUTION
- HABITAT
- CONSERVATION
- MULTIMEDIA
General Description
Elf owls (Micrathene whitneyi) are the smallest owl in the world, with adults measuring 4.9-5.6 in (12.4-14.2 cm) in length and weighing 1.2-1.9 oz (35-55 g). Its back is grayish brown with buff mottling; the belly is grayish white with cinnamon vertical streaks. A prominent white eyebrow stripe encircles cinnamon facial disks, there are no ear tufts, and the eye is yellow. The wings have two white stripes. Elf owls have a short tail with buffy bands. The sexes are alike in plumage, with the female somewhat larger. The plumages remain the same throughout the year. Four months after hatching, juvenile plumage is mottled grayish brown and resembles the adult. Elf owls are nocturnal with higher rates of activity from sunset plus 4 hours and from 4 hours until sunrise. Elf owls spend the non-breeding season in Mexico as far south as Oaxaca. It is thought that elf owls migrate because arthropod food resources are more active farther south during the winter.
Legal Status
The state of California listed the elf owl as endangered in 1980.
Taxonomy
The Elf Owl (Micrathene whitneyi) is a member of the owl family Strigidae. It breeds in the southwestern United States and Mexico, and is the world's smallest owl.
Reproduction
In the LCR MSCP area, elf owls return to breeding grounds in March and leave in September. The elf owl is a secondary cavity nester, relying on cavities excavated by other birds. Throughout the LCR MSCP area, elf owls utilize cavities for nesting in cottonwood, willow, saguaro, and saltcedar trees, formerly occupied by Gila woodpeckers, gilded flickers, and ladder-backed woodpeckers. Typically, pair formation is established when the female accepts food from the male at a cavity of her choice, typically in early May. The female may choose the nest cavity weeks before egg laying occurs. Pair bonds last for approximately 3 months. Typically, mating occurs multiple times per night, over several nights. From the start of cavity selection, the male feeds the female increasingly through the fledging of young. Nests are bare wood bottoms of the cavities. Elf owls have one brood and replace lost clutches. Elf owls lay eggs in late April to late June. Three eggs are typically laid in primary nests over 6 days, with 1-2 eggs laid in replacement nests. The female solely incubates the eggs for 24 days. The female remains on the nest for all but brief periods at dusk and dawn. The hatched young stay in the nest for 28-33 days.
Diet
The major food items are arthropods, consisting principally of insects, including moths, beetles, and crickets. The prey type changes to primarily scarab beetles as the summer rains bring large population of these beetles. There have been a few reports of elf owls eating snakes, lizards, and mice. In the nesting season, adults often cache prey for later consumption by nestlings. Elf owls capture their prey in flight, on the ground, on foliage, on flowers, around outdoor lights, and at hummingbird feeders. Occasionally, they run after the prey on the ground.
Threats
Great horned owls and Cooper’s hawks predate on adults and fledglings. In defense from predators, elf owls cooperatively mob, incessantly vocalize, and physically attack. Fly larvae has been reported parasitizing elf owls.
More Information
Additional information on this species, as well as source documentation, can be found in the species accounts located at this link (PDF). The Conceptual Ecological Model (CEM) can be found here (PDF). Technical Reports on this species can be found here.
Updated December 30, 2016
Elf owl breeding has been documented in three distinct areas of the southwestern United States including: The lower Colorado River, from southern Nevada, eastern California, and western Arizona, west to the Rio Grande River in New Mexico; The Big Bend region of Texas, east to Edwards Plateau; and Dimmit County, Texas, southward, through the Rio Grande River, to Nuevo León, Mexico. Breeding along the lower Colorado River is rarely observed.
In Mexico, there are three distinct year-round and wintering populations of elf owls including: the southern portion of Baja California, which supports a year-round population; Socorro and other Revilla Gigedo Islands, which support a year-round population; and a wintering population located from southwestern Puebla to northern Oaxaca.
The image below shows the distribution range of the elf owl.
In most of its breeding range, the elf owl is associated with mature saguaro cactus and riparian habitat. Along the LCR, elf owls are associated with mature mesquite woodlands and cottonwood-willow riparian areas. In the non-breeding season, elf owls utilize tropical deciduous forests with columnar cacti and arid grassy savanna with columnar cacti.
LCR MSCP Conservation Measures
The Habitat Conservation Plan provides conservation measures specific to each species. Listed below are the species specific conservation measures for the elf owl. Click on the arrows to expand the table.
| ELOW1—Create 1,784 acres of elf owl habitat |
Of the 7,260 acres of created cottonwood-willow and honey mesquite land cover, at least 1,784 acres will be designed and created to provide elf owl habitat. Patches of created habitat will be designed and managed to support cottonwood-willow types I and II and honey mesquite type III that provide habitat for this species. The created habitat will be established in patches as large as possible. At a minimum, however, isolated patches of honey mesquite type III will be created in patches of at least 50 acres, and, of the 5,940 acres of LCR MSCP–created cottonwood-willow, 1,702 acres will be created in patches of at least 50 acres, 2,348 acres will be created in patches of at least 25 acres, and 1,890 acres will be created in patches of at least 10 acres. In addition to the spatial replacement of affected habitat, the quality of created habitat will be substantially greater than affected habitats. Patches of existing cottonwood-willow in the LCR MSCP planning area typically include dense stands of saltcedar that support little vegetative diversity relative to the cottonwood willow land cover that will be created as habitat. Created habitat will be dominated by native riparian trees (i.e., cottonwood and willow trees), support a tree structure corresponding to structural types I and II, support a diversity of plant species, and be created to the greatest extent practicable in patch sizes optimal for supporting the species. The created elf owl habitat will also provide habitat for gilded flickers and Gila woodpeckers that create tree cavities that are used by elf owls for nesting. The design and management criteria described in the conservation measures for the yellow-billed cuckoo (Section 5.7.14 in the HCP) will ensure that created cottonwood-willow stands in structural types I and II will also provide other habitat requirements for this species (e.g., habitat patch size, food requirements). Created habitat, thus, will approximate the condition of the native habitat of the species that was historically present along the LCR. In addition, larger patches of created southwestern willow flycatcher habitat (i.e., greater than 10 acres) that supports cottonwood-willow types I and II could also provide habitat for this species. |
| ELOW2—Install elf owl nest boxes |
Until vegetation has matured sufficiently to attract woodpeckers that are needed to create nesting cavities for the elf owl, structural characteristics of nesting habitat (i.e., snags) will be artificially established. Installation of 2–5 nest boxes on poles or sufficiently tall trees per 250 acres of created habitat will be conducted to replicate the average breeding density of established populations in southwestern United States (Henry and Gehlbach 1999). |
| MRM1—Conduct surveys and research to better identify covered and evaluation species habitat requirements |
Conduct surveys and research, as appropriate, to collect information necessary to better define the species habitat requirements and to design and manage fully functioning created covered and evaluation species habitats. This conservation measure applies to those species for which comparable measures are not subsumed under species-specific conservation measures (Section 5.7 in the HCP). They are not applicable to species for which habitat would not be created under the LCR MSCP Conservation Plan, such as the desert tortoise, relict leopard frog, humpback chub, and threecorner milkvetch. |
| MRM2—Monitor and adaptively manage created covered and evaluation species habitats |
Created species habitats will be managed to maintain their functions as species habitat over the term of the LCR MSCP. Created habitat will be monitored and adaptively managed over time to determine the types and frequency of management activities that may be required to maintain created cottonwood-willow, honey mesquite, marsh, and backwater land cover as habitat for covered species. This conservation measure applies to those species for which comparable measures are not subsumed under species-specific conservation measures (Section 5.7 in the HCP). They are not applicable to species for which habitat would not be created under the LCR MSCP Conservation Plan, such as the desert tortoise, relict leopard frog, humpback chub, and threecorner milkvetch. |
| MRM3—Conduct research to determine and address the effects of nest site competition with European starlings on reproduction of covered species |
Research will be undertaken to determine whether nest site competition with European starlings is a substantial factor limiting the reproductive success of the elf owl, gilded flicker, and Gila woodpecker. If so, experimental programs may be implemented to determine the effectiveness and practicality of controlling starlings. |
| CMM1—Reduce risk of loss of created habitat to wildfire |
Management of LCR MSCP conservation areas will include contributing to and integrating with local, state, and Federal agency fire management plans. Conservation areas will be designed to contain wildfire and facilitate rapid response to suppress fires (e.g., fire management plans will be an element of each conservation area management plan). |
| CMM2—Replace created habitat affected by wildfire |
In the event of created-habitat degradation or loss as a result of wildfire, land management and habitat creation measures to support the reestablishment of native vegetation will be identified and implemented. |
| AMM1—To the extent practicable, avoid and minimize impacts of implementing the LCR MSCP on existing covered species habitats |
To the extent practicable, establishment and management of LCR MSCP–created habitats will avoid removal of existing cottonwood-willow stands, honey mesquite bosques, marsh, and backwaters to avoid and minimize impacts on habitat they provide for covered species. Temporary disturbance of covered species habitats, however, may be associated with habitat creation and subsequent maintenance activities (e.g., controlled burning in marshes and removal of trees to maintain succession objectives). LCR MSCP conservation measures that could result in such temporary disturbances will, to the extent practicable, be designed and implemented to avoid or minimize the potential for disturbance. In addition to implementing AMM3 and AMM4 below, these measures could include conducting preconstruction surveys to determine if covered species are present and, if present, implementing habitat establishment and management activities during periods when the species would be least sensitive to those activities; or redesigning the activities to avoid the need to disturb sensitive habitat use areas; staging construction activities away from sensitive habitat use areas; and implementing BMPs to control erosion when implementing ground disturbing activities. |
| AMM3—To the extent practicable, avoid and minimize disturbance of covered bird species during the breeding season |
To the extent practicable, to avoid and minimize potential impacts on covered bird species, vegetation management activities (e.g., periodic removal of emergent vegetation to maintain canals and drains) associated with implementation of covered activities and the LCR MSCP that could result in disturbance to covered bird species will not be implemented during the breeding season to prevent injury or mortality of eggs and young birds unable to avoid these activities. Table 5-9 in the HCP describes the breeding period for each of the covered species during which, to the extent practicable, vegetation management activities in each species' habitat will be avoided. |
| AMM5—Avoid impacts of operation, maintenance, and replacement of hydroelectric generation and transmission facilities on covered species in the LCR MSCP planning area |
To the extent practicable, before implementing activities associated with OM&R of hydroelectric generation and transmission facilities, measures will be identified and implemented that are necessary to avoid take of covered species where such activities could otherwise result in take. These measures could include conducting surveys to determine if covered species are present and, if so, deferring the implementation of activities to avoid disturbance during the breeding season; redesigning the activities to avoid the need to disturb covered species habitat use areas; staging of equipment outside of covered species habitats; delineating the limits of vegetation control activities to ensure that only the vegetation that needs to be removed to maintain infrastructure is removed; stockpiling and disposing of removed vegetation in a manner that minimizes the risk of fire; and implementing BMPs to control erosion when implementing ground disturbing activities. |
| AMM6—Avoid or minimize impacts on covered species habitats during dredging, bank stabilization activities and other river management activities |
To the extent practicable, before initiating activities involved with river maintenance projects, measures will be identified and implemented that avoid or minimize take of covered species where such activities could otherwise result in take. Such measures could include alternative methods to achieve project goals, timing of activities, pre-activity surveys, and minimizing the area of effect, including offsite direct and indirect effects (e.g., avoiding or minimizing the need to place dredge spoil and discharge lines in covered species habitats; placing dredge spoils in a manner that will not affect covered species habitats). |
Research and Monitoring Activities
LCR MSCP conduct a variety of research and monitoring activities along the LCR encompassing both MSCP and non-MSCP species. For a complete list of all activities, please see the Research and Monitoring Activities web page.
This gallery includes photos of this species. If you require larger photos, please contact our webmaster Michelle Reilly at mreilly@usbr.gov.
